Solar City? Turning Buildings Into Power Plants, Developments from research labs and the renewables sector are driving new trends in urban design, Forbes, Laurie Winkless, https://www.forbes.com/sites/lauriewinkless/2021/04/20/solar-city-

In the past decade, the price of electricity generated by renewables has plummeted, and solar power has led the way. The staggering 89 % drop – from $359 per MWh in 2009, to $40 in 2019 – for utility-scale solar power has been driven by the decreasing cost of producing the photovoltaic modules, and of the various energy storage technologies used to support them. Alongside this, commercial photovoltaic panels – overwhelmingly made from crystalline silicon – are also getting more efficient, with companies like LG and Sunpower producing panels with conversion efficiencies (that is, a measure of how good they are at turning sunlight into electricity) of > 22 %. ** And that energy is certainly worth harvesting. The sun’s radiation delivers more energy to the surface of the Earth in 37 minutes (592 EJ) than the whole world consumes in a year (584 EJ).

According to the International Energy Agency (IEA), the “…buildings and buildings construction sectors combined are responsible for over one-third of global final energy consumption and nearly 40% of total direct and indirect CO₂ emissions”. 

With so many environmental and financial benefits to using solar power, it’s no surprise that it is playing a rapidly-growing role in the world’s energy mix. Large capacity solar farms have been constructed in close to 60 countries, with expansions and additions planned for the coming years. In urban areas where space is at a premium, a different solution is needed.

Rooftops are the obvious choice for urban solar panel installations, and as I’ve written previously, they’re a sizeable resource, representing “… 15 to 35 % of the total land area” in a city. But the availability of rooftops means that they’re often slated for other uses, as a vegetable garden or leisure area, for example. There’s another consideration too – aesthetically at least, most conventional arrays leave a lot to be desired. With architects describing them as “pretty ugly”, or an eyesore, it seems that the ‘look’ of a solar panel can act as a real barrier to its wider adoption in urban architecture. But what if these panels could be made more attractive, or even designed so that they blend seamlessly into the background?

That’s the ultimate goal of building-integrated solar power (BIPV), whereby the building structure itself transformed into a giant photovoltaic generator. There are two main categories of BIPV and many, many potential technologies that could be used to achieve it. Here is just a small sample:

Hit the Roof

For roofing, much of the focus is on solar tiles, sometimes called photovoltaic shingles. These are solar panels that are the size and shape of traditional roof tiles, providing the same structural integrity and weatherproof characteristics, while also generating electricity. Lots of companies are already installing these roofs, with almost all relying on crystalline silicon as the active ingredient, but Tesla’s Solar Roof is probably the one you’ve heard of. Its tiles are made from glass, with slightly different colors and textures available to mimic different roofing materials. A Tesla roof replaces an existing roof in its entirety – it’s not installed on top of it. Despite this, only some of the glass tiles (around 35 %) are photovoltaic. The rest are inactive, but from the ground, they all look the same, which is what gives it a seamless appearance.

There is plenty of debate about just how cost- and energy-efficient these roofs are compared to rack-mounted rooftop arrays. A recent article suggested that “the cost of a solar roof is almost double that of installing a traditional solar system and a roof replacement” and that “…you will get greater long-term savings with a traditional solar panel system.” This is mainly because a solar panel’s orientation (e.g. north, south, east, or west-facing) and installation angle (0° = horizontal and 90° = vertical) can have major impact on how much electricity it can generate over the course of its lifetime. A solar roof has limited options in this regard because the slope of a building roof is fixed.

In contrast, rack-mounted panels can be set at any angle to maximise solar generation. Regardless, solar roofs are increasingly talked-about, especially when it comes to their potential use in heritage or historic buildings in Europe, where preserving appearance is a key priority. Swiss start-up Freesuns recently installed their matte grey solar tiles onto an 18^th century chalet, and Serbian researchers are investigating if these ‘invisible’ photovoltaics could be used on some of Belgrade’s oldest buildings.

Up the wall

For facades in urban areas, color seems to be main focus, with a veritable rainbow of photovoltaic options now commercially available. But changing the color of a solar panel is not straightforward.

Let’s start with crystalline silicon panels, which in their ‘natural’ state tend to appear blue or black. This tells us a bit about how the material is made. The dark blue, sparkly appearance of polycrystalline solar cells results from the geometric crystals that naturally form when molten silicon is allowed to cool slowly. When sunlight falls on them, a small proportion of it is reflected from these crystal edges, rather than being absorbed by them. This reduces the cell’s overall conversion efficiency, but they make up for that by being relatively cheap to produce.

Monocrystalline solar panels, as their name suggests, are each made from a single silicon crystal. They absorb all of the visible light that falls on them, which is why they look black, but they’re considerably more expensive to make. In practical applications, all crystalline silicon solar panels also have an anti-reflective coating applied to them – it reflects blue light, further adding to the blue tint. Manufacturers have used that same principle to achieve a range of different colors simply by changing the thickness of this layer (and therefore, wavelength of light that it reflects). The outcome can be seen on buildings such as Kingsgate House in London and Amsterdam’s Hotel Jakarta, but as it still rather expensive and difficult to do at scale, it is not particularly widespread.

Other researchers and manufacturers are taking a different approach to creating color; one inspired by nature. Germany’s Fraunhofer Institute use a very fine surface texture combined with a thin coating to precisely diffuse sunlight, so that the panel reflects only a narrow band of wavelengths. Just like with butterfly wings, there are no pigments or dyes involved – just clever surface engineering – and yet this approach can provide incredibly bright, vivid colors. In a recent article from Fraunhofer, one of their scientists, Thomas Kroyer, said that “Around 93 percent of light can penetrate this layer, with only around 7 percent being reflected to cause the colour effect.” Company SwissInso have developed a similar technology, and they say that it allows between 85 and 90 % of light through, depending on the chosen color. They’ve already installed their Kromatix™ Solar Glass on schools, universities, homes and office buildings, with many more projects planned.

But while crystalline silicon panels work well for walls or on roofs, they are most often opaque, which renders them unsuitable for use as windows. We need a transparent (or at least semi-transparent) option, and that’s really where thin-film solar materials come in.

Through the glass

Dye-sensitized solar cells (DSSC) have been around for close to 30 years, which makes them the original colorful photovoltaics. Their design was initially inspired by photosynthesis – the process by which plants transform sunlight into energy via the green pigment (chlorophyll) found in their leaves. But rather than a leaf, DSSCs typically start with a porous, transparent film of titanium dioxide nanoparticles. This film can then be coated with a range of different dyes; each one optimized for specific wavelengths of light. When sunlight hits it, it excites electrons in the dye, which then flow into the titanium dioxide.

Though less efficient than silicon solar cells, these cells have multiple advantages. They’re cheap and relatively simple to produce, they’re partially flexible and semi-transparent, and they work under non-direct sunlight. So it’s no real surprise that DSSCs have attracted a lot of attention for use in windows, art installations and shading facades and structures. Dutch designer Marjan van Aubel’s beautiful, dye-based solar cells regularly hit headlines, while those that adorn the convention centre at Ecole Polytechnique Fédérale de Lausanne (EPFL) provide both color and shading to the imposing glass structure. And a group of French researchers are currently working on DSSCs that self-adjust, changing their appearance in response to different lighting conditions.

And finally, there’s the new kid on the thin-film block: perovskites. They can be made from any number of materials; it’s the material’s crystal shape that they all have in common. And they are rather good at transforming sunlight into electricity, with some perovskite cells now reaching efficiencies of 25.5 % in 2020. Considering they’ve only been around since 2009 (when their efficiency was measured to be 3.8 %), that is an astonishingly speedy improvement! As with other solar materials, it’s possible to tune the color of perovskite films by altering their internal structure and texture, or through the application of coatings. The resulting cells can be very eye-catching.

Perovskites can also be made opaque or semi-transparent, and some are flexible. And they can generate electricity with a layer of material just 400 nm thick; that’s about a thousand times thinner than a sheet of printer paper. This hints at one of the main challenges facing perovskite solar cells – can films this thin ever be made sufficiently durable for widespread, long-term outdoor use? Researchers are still searching for that answer.

Potentially the most exciting development in this area are so-called tandem cells, which combine silicon and perovskite in one device. OxfordPV’s latest offering has led to a lot of excitement – it can convert 29.52 % of solar energy that hits into electricity. The company say that their tandem cells will be commercially available sometime in 2022. We’ll have to wait and see.

And if you’re wondering if all this is worth the effort? According to the International Energy Agency (IEA), the “…buildings and buildings construction sectors combined are responsible for over one-third of global final energy consumption and nearly 40% of total direct and indirect CO₂ emissions”. Buildings are intensely damaging to the environment, and building-integrated solar power is one way to start shifting that balance. Yes it’s still in its early stages, and no, it’s not perfect, but if we want to transform buildings from energy consumers into energy producers, we need to think big… or maybe that should be BIPV.

** The very best lab-based single junction silicon solar cells currently reach an efficiency of 26.7 %, which isn’t all that far away from the theoretical limit for this material. Going beyond that limit involved a different approach – scientists and engineers combine solar cells materials into multi-junction devices, and use lenses and reflectors to concentrate the sunlight that hits them. Using this approach, the National Renewable Energy Laboratory (NREL) reached 47.1% efficiency with their six-junction cell. That’s the current world record for solar conversion efficiency.

**

Fraunhofer

BAU 2021 online trade fair: MorphoColour and photovoltaic shingles: Solar technology with the beauty of butterfly wings

Press release / January 11, 2021

Photovoltaic and solar thermal systems are not always considered aesthetically enhancing to a building. The coloured modules, however, being developed at the Fraunhofer Institute for Solar Energy Systems ISE are refreshingly challenging this perspective. Inspired by the phenomen that causes the shimmerings shades of blue or green of the wings of the morpho butterfly, the underlying mechanism of spectrally selective reflectance allows the finished modules to be a homogenously uniform colour. Whether you want gorgeous bright tones or more subdued greys it is possible to design the solar module colour to enhance or blend with the building to which the module will be mounted. These colourful modules will be exhibited at the next BAU trade fair.

Last modified:  January 11, 2021

Generating electricity from the sun via photovoltaic systems is a matter of course today. Solar photovoltaics has become a low-cost renewable energy technology. The appearance of rooftop solar panels has also evolved with advances in technology, and modern solar panels have a sleek design to maximize kerb appeal. Solar panels are made by stringing together many (60+) solar cells sandwiched between a glass front sheet and a laminate polymer backsheet. As there are gaps between the solar cells, you can still see a portion of the backsheet from the front. The colour of backsheet is traditionally white which sticks out against the dark solar cells. Solar panel design can vary based on the make and model. In addition to the cell type of the panel, the backsheet, the frame and presence of „bus-bars“, can affect the final aesthetics of installed panels. Busbars are thin strips that are soldered on solar cells to collect the electricity that is generated by the cells.

Solar modules can be integrated almost invisibly into facades and roofs

Despite this improvement the „look“ of photovoltaic modules is still not a popular design feature among building owners and architects. Particularly when it comes to facades, which are visually more prominent than roofs. But it is important to utilise facades for solar modules if we are to fill the criterion of the German „energy transition“ which estimates a further 2500 square kilometers of additional photovoltaic systems are required.

Researchers from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg have therefore developed visually appealing, colourful modules. The colourful components can be manufactured in the desired colour and integrated almost invisibly into facades or roofs. They can even give the finishing touch to modern buildings with a ventilated curtain-wall facade. “The brainwave behind this development was not to colour the protective glass on modules with pigments, but to imitate the physical effect of butterfly wings,” says Dr. Thomas Kroyer, head of the coating technologies and systems group. If glass was coated with pigments, the modules would lose a greater portion of their efficiency because the light could no longer penetrate unhindered.

Inspired by the blue morpho butterfly

The bright iridescent wing of the morpho butterfly is different. These insects, which are native to the tropical rain forest in Central and South America, create the impression of colour thanks to an optical effect rather than pigments. The wings of this butterfly have an extremely fine surface texture that reflects a narrow range of specific wavelengths, which is to say a certain colour. The Fraunhofer ISE experts apply a similar surface texture and coating to the back of the protective glass on photovoltaic modules using vacuum technology. Depending on the tailoring of the coating, cover glass can be made in say a crisp blue, green, or red. “Around 93 percent of light can penetrate this layer, with only around 7 percent being reflected to cause the colour effect,” explains Thomas Kroyer. The Fraunhofer Research Institute based in Freiburg named its technology MorphoColour after the bright blue morpho butterfly.

Aesthetically pleasing energy-plus buildings

The MorphoColour coated protective glass, produced using vacuum technology, can be laminated to form photovoltaic modules or indeed used in a collector for solar heat generation. There is a real benefit here because both products can be supplied from a single production line – an advantage that should also appeal to end users. In the future, it will be possible to have photovoltaic and solar thermal modules in the same colour, mounted almost invisibly next to each other on the roof or on the facade. When the colour is matched to the rest of the building, the result is an exterior wall with a perfectly uniform finish and a facade that supplies electricity as well as heat. In that sense, future homes can be aesthetically pleasing plus-energy houses, supplying more energy than they consume.

New assembly method prevents unsightly gaps

Colour alone does not make for a visually appealing design. The Fraunhofer researchers found another solution to make photovoltaic systems more attractive: to prevent soldered photovoltaic cells from shimmering through the coloured protective glass, they developed an assembly method that evokes the effect of roof shingles. Roof shingles are laid on top of each other so that the rain runs off. In a similar fashion, the solar technology researchers in Freiburg are now producing photovoltaic cells in strips that overlap by a few millimeters, gluing them together to form a larger module. This creates a homogeneous overall look without unsightly gaps or visible connecting cables. “You can look at our photovoltaic shingles with MorphoColour coating from different angles and still the uniform appearance remains the same.”

The shingled modules will be exhibited at the BAU trade fair, which is taking place online from January 13 to 15, 2021.  

• Fraunhofer Institute for Solar Energy Systems ISE  (ise.fraunhofer.de)
• Press release: Solar technology with the beauty of butterfly wings [ PDF  0.27 MB ] 

https://www.fraunhofer.de/en/press/research-news/2021/january-2021/solar-technology-with-the-beauty-of-butterfly-wings.html

**

Kromatix™

Adding Colour to the Solar Industry

Colour treated glass for photovoltaic (PV) and thermal panel applications involves the application of highly efficient and environmentally friendly nanotechnology surface treatments optimized for solar energy (photovoltaic and thermal). This means our product has no paint or tint, but atomic deposition transforming the solar glass into colour. Kromatix™ technology offers vast new opportunities combining full architectural design flexibility and unparalleled panel aesthetics with optimum panel performance for solar building integration.                               

Application

Kromatix™Grey

Kromatix™ glass is the front glass layer of a solar panel and can be applied to a large variety of solar powered products and technologies. For facade applications we currently experience the highest demand in photovoltaic and thermal applications. 

SwissINSO can deliver Kromatix™ glass stand alone or deliver a complete coloured solar (PV or Thermal) panels in various sizes and thicknesses.   

Kromatix™ is currently available in six colours, Grey, Blue, Blue Green, Orange, Bronze and Brass.

Kromatix™ Technology 

Kromatix™glass is obtained by combining two different surface treatments:

• A multilayered coating is deposited on the inner glass surface by low pressure plasma processes. Its constitutive materials are exclusively characterized by high solar transmittance, minimal absorption and high durability while maximizing high angular colour stability. No pigments or dyes (paint) are used so that the colour does not fade out with the passage of time or due to sun exposure.
• Treatment of the outer glass surface results in diffused reflection. This prevents glare effects and reinforces the masking effect of the solar devices technical parts, further enhancing aesthetics.

Colour Principle

The colours of nature all around us are produced by different aspects of the interaction of light with matter. The most common is light interacting with coloured pigments and dyes which absorb and reflect certain light wavelengths. Colour has however sometimes a purely physical origin as created by diffraction or interference of light. It is a known fact that many butterflies obtain their colour thanks to interference phenomena.

Applying this technique to solar glass a good compromise has to be found, as the higher the reflectance, the lower the transmittance and the energetic performance of the solar device on which the coloured glass cover is installed. This is why the colour changes as the angle changes.

Kromatix™ and Solar Panel Performance

The IFT Certified Kromatix™ Solar Glass is available in various colours. There are no paints nor tints used to colour the glass therefore it remains stable with time and sun exposure and thanks to the unique Kromatix™ technology average transmittance is between 85% and 90% colour depended. The colored solar glass is produced in various dimensions and thicknesses, can be processed in the same way as standard solar glass in order to fit the customer production process.SEE OUR PROJECTSINFO@SWISSINSO.COM

** https://www.sciencemag.org/news/2018/04/solar-cells-work-low-light-could-charge-devices-indoors

Solar cells that work in low light could charge devices indoors

By Robert F. Service Apr. 23, 2018 , 2:10 PM

Imagine never having to charge your phone, e-reader, or tablet again. Researchers report that they have created solar cells that work at a record efficiency for making electricity from the low-intensity diffuse light that is present inside buildings and outside on cloudy days. The solar cells could one day lead to device covers that continually recharge gadgets without ever having to plug them in.

Diffuse light solar cells aren’t new—but the best ones relied on expensive semiconductors. In 1991, chemist Michael Graetzel of the Swiss Federal Institute of Technology in Lausanne invented so-called dye-sensitized solar cells (DSSCs) that work best in dim light and are cheaper than the standard semiconductors. Yet under full sun, the best DSSCs convert only 14% of the energy in sunlight to electricity—versus about 24% for standard solar cells—essentially because the energy comes too fast for DSSCs to handle. When the energy comes at a slower pace, as it does with low-intensity indoor light, Graetzel’s DSSCs could convert up to 28% of the light energy they absorb into electricity.

DSSCs also work a bit differently from standard silicon solar cells. In standard cells, absorbed sunlight kicks electrons on silicon atoms up to a higher energy level, allowing them to skip across neighboring atoms towards a positively charged electrode. There they are collected and shunted into an electrical circuit where they can do work. The departed electrons leave behind vacancies in the atoms called holes that, oddly enough, can also move around. Over time, the holes travel to the negatively charged electrode where they are filled with electrons from the external circuit. This rebalances the charges in the solar cell’s silicon atoms, allowing it to continue to generate electricity.  

DSSCs take things up a notch. They still have two electrodes that collect negative and positive charges. But in the middle, instead of just silicon, they have a different electron conductor, typically a collection of titanium dioxide (TiO₂) particles. TiO₂ is a poor light absorber, however. So, researchers coat the particles with organic dye molecules that are exceptional light absorbers. Absorbed photons of light excite electrons and holes on these dye molecules, just as in the silicon. The dyes immediately hand off excited electrons to the TiO₂ particles, which zip them along to the positive electrode. The holes, meanwhile, are dumped into a charge-conducting liquid called an electrolyte, where they percolate through to the negatively charged electrode.

The problem with DSSCs is that the holes don’t move through the electrolyte very quickly. As a result, holes tend to pile up near the dye and TiO₂ particles. If an excited electron ends up bumping into a hole, they merge, generating heat instead of electricity.

To get around this, researchers have tried to make their electrolyte layers thin, so that the holes don’t have to travel very far to reach their goal. But any imperfections in those thin layers can cause the devices to short, a fatal blow that kills the whole solar cell. Now, Graetzel and his colleagues have now come up with a possible solution. They designed a combination of dye and hole-conducting molecules that wrap themselves tightly around TiO₂ particles, creating tight-fitting layers without any imperfections. That means slow-moving holes have less distance to travel before reaching the negative electrode. The tight layers, they report today in Joule, increase the diffuse light efficiency of their DSSCs to 32%, near the theoretical maximum.

 “It’s really a nice advance,” says Michael Wasielewski, a chemist at Northwestern University in Evanston, Illinois. The new devices still only convert 13.1% of direct sunlight to electricity. But he notes that because the diffuse light efficiency is nearly 20% higher, it raises hopes that new ways might be found to boost the efficiency of the devices under full sunlight. And because DSSCs are far cheaper to produce than silicon solar cells, if they can approach silicon’s efficiency at a lower cost, that should be a winning formula. Until then, diffuse light DSSCs can at least help us power a host of devices without cords, plugs, or external power. Numerous companies are already working to outfit building interiors with an earlier generation of DSSCs. And Graetzel says he believes the new and improved cells will only speed up the adoption of the technology. Posted in:  Chemistry Technology

doi:10.1126/science.aat9682 Robert F. Service Bob is a news reporter for Science in Portland, Oregon, covering chemistry, materials science, and energy stories.

**

Colorful Perovskite Solar Cells: Progress, Strategies, and Potentials

• Hao Wang
• Jia Li
• Herlina Arianita Dewi
• Nripan Mathews
• Subodh Mhaisalkar
• Annalisa Bruno*

Cite this: J. Phys. Chem. Lett. 2021, 12, 4, 1321–1329Publication Date:January 27, 2021https://doi.org/10.1021/acs.jpclett.0c03445Copyright © 2021 American Chemical SocietyRIGHTS & PERMISSIONS

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5LEARN ABOUT THESE METRICSShare Add to ExportRISRead OnlinePDF (11 MB)SUBJECTS:

• Thickness,
• Color,
• Layers,
• Electrodes,
• Perovskites

The Journal of Physical Chemistry Letters

Abstract

In the past few years, a large variety of perovskite solar cells (PSCs) with vivid and well-distinguished color hues have been demonstrated. In this Perspective, we compare different strategies employed to realize colorful PSCs both in opaque and semitransparent designs. The approaches used to modulate the PSCs’ colorful appearance can be divided into two main categories: the first one based on the modifications of their internal layers (i.e., absorber, electron- and/or hole-transporting layers, and electrodes), while the second is based on the addition of external colored or nanostructured films to the standard PSCs. The advantages and bottlenecks of each strategy are discussed in terms of PSCs’ color tunability, transparency, photovoltaic performances, fabrication processes feasibility, and scalability, in view of suitable applications in an urban context for building-integrated photovoltaics.

1. Susmita Paul, Katsuhiko Ariga, D.D. Sarma, Somobrata Acharya. Dimension-controlled halide perovkites using templates. Nano Today 2021, 39 , 101181. https://doi.org/10.1016/j.nantod.2021.101181
2. Jia Li, Herlina Arianita Dewi, Hao Wang, Jiashang Zhao, Nidhi Tiwari, Natalia Yantara, Tadas Malinauskas, Vytautas Getautis, Tom J. Savenije, Nripan Mathews, Subodh Mhaisalkar, Annalisa Bruno. Co‐Evaporated MAPbI 3 with Graded Fermi Levels Enables Highly Performing, Scalable, and Flexible p‐i‐n Perovskite Solar Cells. Advanced Functional Materials 2021, 4 , 2103252. https://doi.org/10.1002/adfm.202103252
3. Sangho Kim, Junsin Yi, Joondong Kim. Bifacial Color‐Tunable Transparent Photovoltaics for Application as Building‐Integrated Photovoltaics. Solar RRL 2021, 9 , 2100162. https://doi.org/10.1002/solr.202100162
4. Cong Chen, Shijian Zheng, Hongwei Song. Photon management to reduce energy loss in perovskite solar cells. Chemical Society Reviews 2021, 50 (12) , 7250-7329. https://doi.org/10.1039/D0CS01488E
5. Saikat Bhaumik, Manav Raj Kar, Bhaskar N. Thorat, Annalisa Bruno, Subodh G. Mhaisalkar. Vacuum‐Processed Metal Halide Perovskite Light‐Emitting Diodes: Prospects and Challenges. ChemPlusChem 2021, 86 (4) , 558-573. https://doi.org/10.1002/cplu.202000795

** Published: 08 June 2020 Nature Energy

Photochromic dye-sensitized solar cells with light-driven adjustable optical transmission and power conversion efficiency

• Quentin Huaulmé, 
• Valid M. Mwalukuku, 
• Damien Joly, 
• Johan Liotier, 
• Yann Kervella, 
• Pascale Maldivi, 
• Stéphanie Narbey, 
• Frédéric Oswald, 
• Antonio J. Riquelme, 
• Juan Antonio Anta & 
• Renaud Demadrille 

Nature Energy volume 5, pages468–477 (2020)Cite this article

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Abstract

Semi-transparent photovoltaics only allow for the fabrication of solar cells with an optical transmission that is fixed during their manufacturing resulting in a trade-off between transparency and efficiency. For the integration of semi-transparent devices in buildings, ideally solar cells should generate electricity while offering the comfort for users to self-adjust their light transmission with the intensity of the daylight. Here we report photochromic dye-sensitized solar cells (DSSCs) based on dyes with a donor-π-conjugated-bridge-acceptor structure where the π-conjugated bridge is substituted by a diphenyl-naphthopyran photochromic unit. DSSCs show change in colour and self-adjustable light transmittance when irradiated and demonstrate a power conversion efficiency up to 4.17%. The colouration–decolouration process is reversible and these DSSCs are stable over 50 days. We also report semi-transparent photo-chromo-voltaic mini-modules (active area of 14 cm²) exhibiting a maximum power output of 32.5 mW after colouration.

** Here’s how much space U.S. cities waste on parking: In cities that are struggling to find space to build affordable housing, a simple solution might be found in the vast areas set aside for storing cars. In Seattle, there are around 1.6 million parking spaces–more than five for every household in the city. Des Moines, a much smaller city, also has roughly 1.6 million parking spaces, or 19.4 per household. The small town of Jackson, Wyoming, has 27.1 parking spots per household. 07-17-18, Fast Company WORLD CHANGING IDEAS,

A new report calculates, for the first time, exactly how many parking spots are in five cities–New York, Philadelphia, Seattle, Des Moines, and Jackson–and gives a sense of how much money and land is being wasted on car storage. It’s data that cities don’t have now, because it’s hard to gather a comprehensive list of spots–not only the ones on streets but in garages and on private land. The report analyzes satellite data to identify some parking spots, pulls on-street parking statistics from city records, and finds other off-street parking in parcel data. The basic finding: Cities have far more parking spaces than they need.

Only in New York City, where there are around 1.9 million parking spaces for the five boroughs, are there more homes than parking spots. Philadelphia has more than 2 million spots, or 3.7 per household.

If some drivers still have the perception that there isn’t enough parking, that’s likely because parking is underpriced or free, says Eric Scharnhorst, a principal data scientist at the startup Parkingmill, who wrote the report for the Research Institute for Housing America, an arm of the Mortgage Bankers Association.

“A lot of times, I’m guilty of this too: If I’m looking for a parking space and I know the on-street stuff is provided for free, or it’s less expensive per hour to park on the street than on the adjacent lot or garage, I’ll circle the street to try to get a deal, even though I know there’s an open spot in the garage or in the parking lot,” he says. “That also influences traffic–there’s more than one person circling the block looking for a deal.”

Parking garages are typically underused–one garage in downtown Des Moines was 92% empty in the middle of the day–but cities spend millions to build the structures. The report estimates that among the five cities analyzed here, parking was worth roughly $81 billion. In Jackson, Wyoming, the estimated cost of parking for each household was $192,138.

City planners are beginning to recognize the problem. “I think there’s a lot of inertia in the system, in the personnel who write the rules for cities, but I’ve seen that starting to change,” says Scharnhorst. “The generation [of planners] coming up is aware of this. A lot of them want to live close to work so that they don’t even have to park anywhere, they can just get there another way.”

Hartford, Connecticut, has completely eliminated parking minimums, the rules that say any developers need to include a certain amount of parking with any new building. Minneapolis, Nashville, Kansas City, and dozens of others have eliminated parking minimums in at least one neighborhood. In Seattle, the city council passed a bill in April that reduces parking requirements for developers to build affordable housing and “unbundles” parking from leases in new developments so renters and buyers don’t have to pay for spaces that they don’t actually use. “Decoupling the cost is a really clean, market-driven, enlightened way to reduce the cost of all housing,” says Scharnhorst.

Americans have been driving less over the last decade, especially in cities, and as ride-hailing increases–and eventually self-driving cars–even fewer people will own cars. The vast urban area now devoted to car storage could be put to higher use. In Seattle, which is in dire need of new affordable housing, 40% of the land area is currently used for parking.

“It’s no secret in the development world that parking lots are just land banks just waiting to be turned into something else,” Scharnhorst says.

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world’s largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley, and contributed to the second edition of the bestselling book “Worldchanging: A User’s Guide for the 21st Century.”  More

**

Cars take up way too much space in cities. New technology could change that.

By: Brad Plumer, https://www.vox.com/a/new-economy-future/cars-cities-technologies

Javier Zarracina/Vox

When we talk about the problems associated with cars and transportation, we often focus on fatal accidents, or air pollution, or traffic jams.

We less frequently consider how much sheer space cars take up in America’s cities. But let’s pause to give this some thought.

There’s the space the cars themselves occupy. The average car, two hulking tons of steel, is 80 percent empty when it’s being driven by a single person. And most of the day, cars are totally empty, sitting unused. That, of course, requires space for parking: There are a billion parking spots across the United States, four for every car in existence. Plus, there are all the paved roads crisscrossing our cities. Add it up, and many downtowns devote 50 to 60 percent of their scarce real estate to vehicles:

It all seems rather inefficient and wasteful. If cities could reclaim even a fraction of this land from vehicles, they could build more housing, or stores, or parks, or plazas. For cities struggling with housing shortages and soaring rents, such as San Francisco and New York City, the gains would be staggering.

Some cities are already tinkering around the margins here — looking, for instance, to cut down on excessive parking requirements or boost mass transit and free up land for development. But new technology could push this even further. Ride-sharing services like Uber and Lyft already hint at a world in which cars are utilized more efficiently and take up less room in aggregate. And if self-driving vehicles become widespread, cities could in theory shrink their transportation footprint even more dramatically.

This world no longer seems so far away. A recent report from the Rocky Mountain Institute argued that the era of private car ownership may peak within a decade, as new networks of shared, electric, possibly autonomous vehicles become cheaper. Instead of buying a car, you can simply buy a ride whenever you need one. That shift has the potential, at least, to revolutionize our streets.

The trick is figuring out how to redesign cities accordingly. Recently, San Francisco sketched out a forward-looking plan to take advantage of these new transportation options and shrink the amount of space devoted to cars. With smaller streets and fewer parking spots, the city would have more land to work with — to build more affordable housing, say. If it works, it could be the start of an important new trend.

San Francisco has an audacious plan to reclaim land from cars

Earlier this year, the Department of Transportation held a contest asking dozens of local governments to submit visions for a “city of the future” that incorporate things like self-driving cars to tackle problems like congestion and climate change.

Columbus, Ohio, ended up winning the contest with a detailed plan to improve mobility in low-income areas. But let’s take a closer look at San Francisco’s submission, because it’s a great exploration of how cities might use new tech and business models to take back scarce land from cars.

The proposal starts by observing that San Francisco currently has 440,000 on-street parking spaces — the same amount of land as the Golden Gate Park and 120 Transamerica buildings. And much of that land sits empty much of the time. “Our plan,” the proposal notes, “would phase in innovative technologies that allow us to repurpose public space currently under-utilized as parking into affordable housing, small parks and pedestrian amenities.”

The first step would be to make ride-sharing services (including, but not limited to, Uber and Lyft) more convenient and accessible to residents. After all, if people can use these cars for their transportation needs, or combine them with masstransit options, they wouldn’t need nearly as much street parking. And because each of these cars serves multiple passengers, they take up less space on the road.

In phase one, San Francisco planned to shift 10 percent of single-occupancy vehicle trips to transit and ride hailing. To do so, the city proposed partnering with the University of California Berkeley and various tech companies to work out ways to:

1) Provide incentives to shift people from their own cars into car sharing: That might mean designating certain road lanes as only available for ride sharing, making them the faster option. It might also entail seamlessly integrating car sharing, bike sharing, and public transit by creating a single simple mobile app that combines routing, scheduling, and payment for all of those services.

2) Make these services more affordable: That might involve providing low-income residents with access to smartphones and banking services, as well as providing free public wifi so that all could use these services. It would also mean finding ways to lower the price of car sharing — say, by deploying larger six-person passenger vans to cut costs below what an Uber or Lyft ride currently costs.

3) Eventually move to automated electric vehicles: If self-driving cars and buses eventually become a reality, they too could be connected into a centralized network, making sharing even easier. In theory, these vehicles could also reduce fatal collisions (assuming that self-driving technology proves safer) and would also eliminate air pollution (assuming that the cars were all electrified rather than running on gasoline).

The proposal offered an illustration of how these different phases would unfold. Note that over time, the amount of land required for parking shrinks as people move from a vehicle ownership model to a transportation service model that encompassed everything from cars to Muni buses to delivery vans:

Timothy Papandreou, the former head of the San Francisco Municipal Transportation Agency’s Office of Innovation, described the goal to the Washington Post in June: “We can move the same amount of people with a tenth of the vehicles. ... It’s really going to open up our minds. We’re not going to need to have all that excess road space.”

Now, San Francisco didn’t win the federal contest or the $50 million grant that came with it. But SFMTA spokesperson Paul Rose told me they’re still looking to move forward with many of the plan’s components. The city is applying for another federal grant to launch pilot programs around “connected carpool lanes, smart traffic signals, autonomous shuttles, dynamic carpool pick-up curbs, connected Vision Zero corridor, and Congestion Toll System,” Rose said. “We expect a decision this month on this application.”

We shouldn’t underrate the challenges here. Reducing the number of vehicles on the road will require persuading people to give up their privately owned cars and shift to a pure sharing model. That’s not easy. It involves changing some deep-seated behaviors, and policymakers and companies will have to get the incentives just right. If ride sharing remains unaffordable, or if people simply don’t want to give up their cars, the plan could easily stumble.

Still, San Francisco has all the reason in the world to try. The city has sharp geographic constraints, and skyrocketing housing prices are making the area unaffordable for many. Reformers often focus on changing the Bay Area’s zoning laws to build more housing on existing land, and that’s no doubt part of a solution. But reclaiming vehicle space for housing could prove an equally appealing concept.

Self-driving cars could free up an enormous amount of room

San Francisco’s transit officials aren’t the only ones thinking about how new tech might decrease the amount of space that cars take up. A fascinating recent study by two British engineering firms, Farrells and WSP|Parsons Brinckerhoff, looked at how London’s streets might be entirely redesigned if self-driving cars ever became a reality.

That study imagined a world in which the autonomous vehicles (AVs) of the future are shared rather than owned — you call for an AV, and it zips right to your door. The AVs themselves are either always on the road, picking up and dropping off passengers, or charging/refueling/parking in a few centralized locations. As such, there’s simply less need for street parking.

What’s more, if all the cars on the road were autonomous, they could take up far less space on the road. Vehicles navigated by robots could nestle closer together without fear of rear-ending each other. If collisions became more rare, the cars themselves could be smaller and thinner, taking up less space. City planners could reduce the width of streets or even cut back on the number of lanes without greatly affecting travel times.

If you pushed this far enough, the study notes, a city like London could gain another 15 to 20 percent of developable area. “This is primarily due to the removal of almost all parking spaces, but also because of roadspace simplification that will save space.”

The authors of the paper sketch out a few visions of what this might look like in London. Like so:

Or like so:

“Of the estimated 8,000 hectares of central London land occupied by parked cars today, it is reasonable to assume that 50-70% — potentially more than 5,000 hectares — could be released once AVs are commonly in use,” the study notes. Replacing those spots with housing or other structures would be worth tens of billions of dollars.

Of course, this is just a vision of what could be — someday. There are tons of hurdles in getting there. For starters, despite all the hype, there are no autonomous vehicles yet available that can handle the range of surprises that might pop up in an urban environment on a daily basis. As I’ve written before, the toughest thing for an autonomous vehicle to handle is other people — particularly reading and reacting to pedestrians, cyclists, and other human drivers. So we’re a ways from true self-driving cars that require no human intervention. It might be years; it might be decades.

What’s more, the transition is likely to be messy. Self-driving cars are most valuable when all the cars on the road are self-driving (that’s when you can get these cars to platoon closely together, for instance, or move more quickly through intersections). As long as there are still some human drivers on the road, though, it’s much harder to get the full benefit from autonomous vehicles. Perhaps the shift will happen naturally, as insurance rates for “manually driven” vehicles go up. Or perhaps cities will have to force the transition through policy.

So for now, think of this report as more of a utopian daydream — the culmination of a slow change in vehicle technology that will eventually let cities devote less space to vehicles and more space to, well, everybody else.

Cities can reclaim vehicle space in low-tech ways, too

Up until now, we’ve mostly been looking at newfangled technology: connected ride-sharing systems and autonomous vehicles. But it’s worth adding that cities don’t have to wait for Silicon Valley to come along before they can reclaim space from cars. There are plenty of low-tech solutions, too, from boosting mass transit to promoting walking and cycling to simple changes in parking policy.

Just as one example, Donald Shoup, an economist at UCLA, has long argued that cities have overbuilt and over-mandated parking. They do this partly by providing free street parking for all. But perhaps more importantly, many cities require all new developments to include specified large numbers of added parking spaces.

This is essentially a mandate for more parking — even if the demand isn’t there. In Washington, DC, the underground spots many developers build to comply with these minimum requirements cost between $30,000 and $50,000 each. It ends up driving up housing prices. And, of course, it means less space for other purposes.

Shoup has argued for a whole spate of changes in parking policy. But one of his simplest recommendations is to simply do away with minimum requirements for off-street parking for new buildings. “I’m pro-choice,” he told Vox. “Let the developers build however many parking spots they want.” (Developers would no doubt still build parking spots to accommodate demand — they just wouldn’t be required to build more than the market could bear.)

It’s not as sexy as a city full of shared, autonomous, connected, electric vehicles. But it’s the same principle. Cars take up a lot of space. One way to make cities better and more prosperous would be to find ways to reduce that space.

Further reading:

• Alissa Walker did a great interview with SFMTA’s Timothy Papandreou about San Francisco’s smart city proposal here. (He has since left SFMTA to join Google X.)
• Tim Lee has written the economic case for allowing many more people to live in cities like San Francisco and New York. Meanwhile, here are some other lessons on boosting housing supply from Seattle and Tokyo. Reclaiming land from vehicles is just one component here.
• Donald Shoup explained to us why free parking is bad for everyone. And Clive Thompson wrote a nice piece for Mother Jones earlier this year on how policymakers and technologists are dreaming up ways to downsize parking.
• Here’s a piece by David Roberts on the transformative potential of self-driving cars. And here’s a piece I wrote on why self-driving cars might be much further away than many optimists think.

This story is part of The new new economy, a series on what the 21st century holds for how we live, travel, and work. https://www.vox.com/a/new-economy-future/cars-cities-technologies

**

You’d Never Guess This NYC Townhouse Is a Passivhaus

When Baxt Ingui does a renovation, you never can tell.

By Lloyd AlterPublished July 21, 2021 01:39PM EDTFact checked by Haley Mast

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The thing about these renovations of New York townhouses by Baxt Ingui Architects is that they don’t look like what people expect Passivhaus renovations to look like. Many people think there will be teensy windows that don’t open, and instead, they are full of light, air, and openness.

Michael Ingui tells Treehugger that sometimes he doesn’t even tell clients they are getting the Passivhaus EnerPHit renovation standard; they are not the type to care about the cost of heating or cooling. He does tell them the house will be incredibly quiet and comfortable thanks to the careful sealing, thick insulation, and triple-glazed windows. Clients like the fact that there is a constant supply of filtered fresh air, particularly when forest fires are affecting air quality even in New York City. And then there is a big benefit for a townhouse in the city: When you seal a party wall so tightly that the air can’t get through, neither can the bugs.

The Carroll Gardens Passive Townhouse is a good example of how architects can deliver all the benefits of Passivhaus in an old New York townhouse. According to the architects:

“The house, originally built in the late 1800s, had an intact brownstone façade and wood cornice, while much of the historical interior character had been modified or damaged, including a sagging floor structure and missing architectural details. The team, including Michael Ingui and Maggie Hummel of Baxt Ingui Architects, Cramer Silkworth of Baukraft Engineering, and Max Michel of M2 Contractors, worked collaboratively to create a house that blended the historic proportions of the townhouse with a number of modern, sculptural elements.”

The “electrify everything” and the heat pump crowds will like this house; it’s got a heat pump water heater, clothes dryer, and HVAC. Heat pumps are easy in a Passivhaus because the loads are so small. The architects explain:

“Through Passive House detailing and insulation, the house requires almost no heat, regardless of how cold it is during the Northeast winters. We were able to eliminate the radiators and replace them with a system that uses minimal ductwork.”

Notably, the house also has an induction cooktop. Some Baxt Ingui clients insist on giant commercial-style gas ranges, but Ingui tells Treehugger they are making headway convincing clients that induction ranges are fine.

The Carroll Gardens Passive House puts paid to the idea that Passivhaus designs can’t have lots of natural light. I used to say “the best window isn’t as good as a lousy wall” but that’s no longer true when you are talking about these high-performance Passivhaus windows from Zola, which have R values of up to R-11. The result: lots of natural light.

 “Since space is so highly valued in a narrow townhouse, the team paid close attention to the floor openings that were created at the rear parlor and the stairwell in the center of the hall. It was important that these openings allow light into the middle of the home and create a continuously open and airy experience as you ascend through each floor. A mix of natural wood elements helped to create an environment that is both modern and warm.”

The Carroll Gardens Passive Townhouse, and much of the work of Baxt Ingui, provide a great demonstration of why the Passivhaus approach makes so much sense in these times. While this is a 4,058-square-foot luxury renovation, the principles are universal. Instead of being net-zero, it needs almost no heating or cooling at all. It doesn’t get fist pumps for heat pumps, because the heat pumps it has make a trivial contribution compared to the real work being done by the fabric of the house itself.

And don’t forget the contribution of the urban form and building type; on a narrow townhouse, the biggest surfaces, the sidewalls, are shared, significantly reducing heat loss. And it’s dense enough that you don’t have to drive to get a quart of milk.

It’s why I keep coming back to Passivhaus—because the first thing we have to do is reduce demand for energy, which makes it so much easier to get to zero carbon emissions. Everything else is just a distraction.

**

You’d Never Guess This NYC Townhouse Is a Passivhaus

When Baxt Ingui does a renovation, you never can tell.

By Lloyd AlterPublished July 21, 2021 01:39PM EDTFact checked by Haley Mast

• Share
• Twitter
• Pinterest
• Email

News

• Environment
• Business & Policy
• Science
• Animals
• Home & Design
• Current Events
• Treehugger Voices

The thing about these renovations of New York townhouses by Baxt Ingui Architects is that they don’t look like what people expect Passivhaus renovations to look like. Many people think there will be teensy windows that don’t open, and instead, they are full of light, air, and openness.

Michael Ingui tells Treehugger that sometimes he doesn’t even tell clients they are getting the Passivhaus EnerPHit renovation standard; they are not the type to care about the cost of heating or cooling. He does tell them the house will be incredibly quiet and comfortable thanks to the careful sealing, thick insulation, and triple-glazed windows. Clients like the fact that there is a constant supply of filtered fresh air, particularly when forest fires are affecting air quality even in New York City. And then there is a big benefit for a townhouse in the city: When you seal a party wall so tightly that the air can’t get through, neither can the bugs.

The Carroll Gardens Passive Townhouse is a good example of how architects can deliver all the benefits of Passivhaus in an old New York townhouse. According to the architects:

“The house, originally built in the late 1800s, had an intact brownstone façade and wood cornice, while much of the historical interior character had been modified or damaged, including a sagging floor structure and missing architectural details. The team, including Michael Ingui and Maggie Hummel of Baxt Ingui Architects, Cramer Silkworth of Baukraft Engineering, and Max Michel of M2 Contractors, worked collaboratively to create a house that blended the historic proportions of the townhouse with a number of modern, sculptural elements.”

The “electrify everything” and the heat pump crowds will like this house; it’s got a heat pump water heater, clothes dryer, and HVAC. Heat pumps are easy in a Passivhaus because the loads are so small. The architects explain:

“Through Passive House detailing and insulation, the house requires almost no heat, regardless of how cold it is during the Northeast winters. We were able to eliminate the radiators and replace them with a system that uses minimal ductwork.”

Notably, the house also has an induction cooktop. Some Baxt Ingui clients insist on giant commercial-style gas ranges, but Ingui tells Treehugger they are making headway convincing clients that induction ranges are fine.

The Carroll Gardens Passive House puts paid to the idea that Passivhaus designs can’t have lots of natural light. I used to say “the best window isn’t as good as a lousy wall” but that’s no longer true when you are talking about these high-performance Passivhaus windows from Zola, which have R values of up to R-11. The result: lots of natural light.

 “Since space is so highly valued in a narrow townhouse, the team paid close attention to the floor openings that were created at the rear parlor and the stairwell in the center of the hall. It was important that these openings allow light into the middle of the home and create a continuously open and airy experience as you ascend through each floor. A mix of natural wood elements helped to create an environment that is both modern and warm.”

The Carroll Gardens Passive Townhouse, and much of the work of Baxt Ingui, provide a great demonstration of why the Passivhaus approach makes so much sense in these times. While this is a 4,058-square-foot luxury renovation, the principles are universal. Instead of being net-zero, it needs almost no heating or cooling at all. It doesn’t get fist pumps for heat pumps, because the heat pumps it has make a trivial contribution compared to the real work being done by the fabric of the house itself.

And don’t forget the contribution of the urban form and building type; on a narrow townhouse, the biggest surfaces, the sidewalls, are shared, significantly reducing heat loss. And it’s dense enough that you don’t have to drive to get a quart of milk.

It’s why I keep coming back to Passivhaus—because the first thing we have to do is reduce demand for energy, which makes it so much easier to get to zero carbon emissions. Everything else is just a distraction.