Clean Heating and Cooling: Ground Source and Air Source Heat Pumps

Ground-Source Heat Pump

Ground-source heat pump  (GSHP) — also referred to as geothermal heat pump — systems provide space heating and cooling, and, in some cases, hot water for residential and commercial buildings. The technology uses an indoor heat pump unit and a heat exchanging ground loop buried underground (or underwater) to transfer thermal energy between and among the ground and the building.

The variation in subsurface and/or groundwater temperatures remains constant across seasons — typically around 55°F, which allows ground-source heat pump systems to reach coefficients of performance of between 3 to 6.

  • When operating in heating mode, GSHP systems transfer thermal energy from the ground (or groundwater) to the building.
  • While when operating in cooling mode, the systems transfer thermal energy from the building to the ground (or groundwater).

GSHP systems are typically sized to provide 100% of the heating and cooling loads for a residential or commercial building. In some cases, though, these systems are sized below peak heating or cooling load – and installed with auxiliary electric resistance heat or cooling towers – to reduce installed costs.

There is significant variation in how the ground loop component is designed and installed, which affects project costs and efficiencies:

  • Closed-loop systems use a ground loop (typically made of polyethylene or PVC piping) that circulates water or antifreeze to exchange heat with the ground or a groundwater source. For closed-loop residential and smaller commercial systems, horizontal “slinky” configurations are often used. Vertical configurations, which can have column wells of up to 400 feet deep, are often used for large commercial systems. Closed-loop systems can also be submerged in bodies of water.
  • Open-loop systems circulate water for heat extraction and rejection directly from local groundwater sources. This can reduce the installed cost due to less piping and enhance system efficiency due to improved heat transfer. Ground-source heat pumps systems can also be designed as direct exchange systems, which circulate a refrigerant through a copper pipe instead of a typical ground loop. Direct exchange systems are highly efficient at heat extraction and rejection.
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Image courtesy Remodel Calculator

Air-Source Heat Pump

Heating and cooling systems use a lot of energy. Air-source heat pumps (ASHPs) are an efficient way to move heat between the outside and inside of a residence to keep it a comfortable temperature all year round. ASHPs have been used for many years in nearly all parts of the US. Recent technology advancements now make them a strong alternative for space heating in colder regions.

Today’s ASHP can reduce electricity use for residential or business heating by approximately 50% and reduce harmful GHG emissions. They also dehumidify better than standard central air- conditioners, resulting in less energy usage and more cooling comfort in summer months. They are quiet to operate and highly efficient, because they move heat rather than convert it.

Types of air-source heat pumps include:

  • Ducted vs. ductless: Ducted systems simply use ductwork. They are central systems that provide heating and cooling through ductwork. If a home already has a ventilation system or the home will be a new construction, ASHPs are an option to consider.
  • Ductless heat pumps, also known as mini-splits, consist of two units — a slim outdoor condenser and an indoor air handler. This indoor unit is connected to the outdoor compressor through a small opening in the wall or ceiling behind it. This means that mini splits don’t require ductwork to carry warm or cold air throughout the home. No ductwork means that mini-splits are very space-saving and flexible in where they can be placed, making them perfect for renovations and home additions. Systems can be single or multi-zone. Single-zone heat or cool one room while multi-zone have two or more indoor air handlers connected to an outdoor condenser allowing you to heat or cool individual rooms, hallways, and open spaces.

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Solar Thermal (Hot Water)

Solar hot water is a renewable power alternative that relies on the sun’s heat energy to produce hot water for homes and businesses. It uses roof-mounted solar collectors to heat cold water. When the water is hot enough and ready to use, pipes transport the water back to a hot water tank. And if a solar hot water (solar thermal) system cannot keep up with the heat demand, a simple, automatic control system enables the conventional water heater to provide supplemental hot water.

Solar energy is a very real and effective solution for homeowners and business owners who live in northern climates. A solar hot water system works when the sun is out — even on cloudy days. Depending on the cost of energy, the amount of sunlight and your typical hot water usage, solar hot water can be a very affordable power source. In fact, in a typical residential installation, electric hot water system users can save as much as 2,800 kilowatt-hours annually, or up to 20% on their electric bill.

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Benefits of Biomass: High-Efficiency, Low-Emission Wood Heating Systems

New high-efficiency biomass systems are automated and cleaner burning. Several characteristics affect the performance of biomass fuel, including the heat value, moisture level, chemical composition, and size and density of the fuel. In essence, more efficient combustion means less fuel is required.

Incentives help offset the cost of replacing or supplementing existing systems and installing new systems. An interesting curriculum from the NEED Project offers many details about switching to biomass as a home and residential energy source.

clean heating and cooling

Graphic courtesy of Canadian Biomass

Final Thoughts

For full details on the NYSERDA initiatives to promote clean heating and cooling, review all documents associated with the Clean Heating and Cooling Community Campaigns PON 3922.