A geothermal residential building is being built in New York: it will receive heat from a hole in the ground

In fact, there will be 322 holes, each about 10 centimeters across and exactly 152 meters deep. If it turns out to be deeper, New York State will consider it a mining project. These openings form the core of a ground source heat pump system. This is expected to reduce carbon emissions by 53% compared to a building using conventional heating systems. When completed in 2025, the facility will be one of the largest residential buildings in the US using this technology.

The temperature underground is always around 13 degrees Celsius. This is why ground source heat pumps are so economical.

Buildings account for about 8% of global carbon emissions

This is mainly due to the burning of fossil fuels for heating. And heat pumps are an important tool for making homes cleaner. Spending on residential heat pump systems rose 9,6% to $64,3 billion globally last year amid a push to electrify much of the international economy. The Brooklyn project will be an important test for Lendlease Corp. This Australian developer is building a geo-exchange system at 1 Java Street. This is an all-electric residential complex located along the Greenpoint waterfront in Brooklyn.

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“We no longer want to use natural gas in any of our buildings,” said Sarah Neff, head of sustainability at Lendlease Americas. If the 1 Java system works, they plan to use geothermal heat pumps in future projects in the US. Lendlease said its geothermal system would increase construction costs by about 6%. Part of these costs will be covered by a $4 million government grant.

1 Java Street will be one of the largest buildings in the US to use a geothermal heat pump system

It works by moving heat between the inside and outside of a building. And it can be used for both heating and cooling. More common direct air systems use an electric compressor. It pressurizes the liquid refrigerant within closed piping coils and has pressure relief valves. In summer, the warm indoor air cools down as the heat energy is absorbed by the liquid, which evaporates. The compressor puts pressure on the gas, making it even hotter as it enters the outdoor coils. The air outside then absorbs some of this heat energy as the refrigerant cools and condenses back into a liquid. The valves reduce the pressure on the liquid, which is cooled, returning inside to repeat the cycle. In winter, the process goes in the opposite direction. The key point is that adjusting the pressure can make the liquid hotter than outside air in summer. And cooler than outside air in winter.

Geothermal systems use the same basic principles. But they are based on the fact that the temperature underground stays around 13°C, no matter how hot or cold the air above is. In the summer, water mixed with an additive that prevents freezing and corrosion is pumped through pipes into wells. There it cools and then rises to cool the building. In cold winter weather, stable temperatures underground can bring water temperatures up to 13°C. And then an electric heater makes it even warmer. And water is pumped through the building for heating.

The building will be fully electric (including induction cookers)

For the water supplied to the apartments, a constant underground temperature will be used to bring it up to 13 °C. And then the electric boiler will make it hot enough for showering and washing dishes. 13-degree water in a closed system will be used for temperature control instead of electric air conditioners or gas heating.

Although 1 Java will rely more on electricity than a normal building, it will need less of it. This is because electric heat pumps are more energy efficient than current heating systems.

“In cold climates, an all-electric building without such a system is not financially feasible,” said Walsh, project director.

Installing geothermal systems is usually significantly more expensive than installing other heat pumps. And the necessary earthworks make it difficult to install them in existing buildings. Geothermal heat pumps are more common in large commercial buildings than in single family homes. And are becoming increasingly popular with developers because the systems require less energy to operate. And they are more profitable in the long run, according to Lewis Williams, an analyst at BloombergNEF.

But the global fight to curb climate change is making heat pumps more popular. The fact is that they are completely electric and eliminate the need for gas heating.

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Heat pump spending has doubled since 2015 and demand will continue to rise

“Heat pumps are becoming the most important part of the building decarbonization solution,” Williams said.

Utilities are also finding ways to use ground source heat pumps in their networks. The National Network announced one such project in September in Massachusetts. and Vermont Gas Systems Inc. is also planning another one. Late last year, the New York regulator asked the state's largest utilities to come up with their own plans to implement the technology.

In suburban Boston, Eversource Energy is installing a ground source heat pump system that uses grid design. It will provide heating and cooling for 39 buildings in the same area. It is the first utility company in the US to try this approach. It is expected to reduce both customer bills and carbon footprint.

This project will connect residential and commercial buildings with more than 100 wells that are up to 180 meters deep. Each building will have its own heat pump. The system is planned to be put into operation before the start of the heating season next winter. This was announced by Nikki Bruno, Vice President of Green Technologies Eversource. This is expected to cost between $10 and $12 million.

The system will consume much less electricity for cooling than conventional air conditioners. And this reduces customer bills in the summer. During the winter, people who use gas heating will likely see some savings as well. About 24% of Massachusetts homes are heated with some form of fuel oil. And their owners will see significant cost savings. Eversource considers this a test and says it can't provide more specific savings estimates just yet. But expects the average household consumer's spending to drop by about 60%.