German manufacturer GEA Heating & Refrigeration Technologies (GEA HRT) has provided a number of examples showing that combining ammonia (NH3/ R717) heat pumps with district heating can be a key way to bring down energy consumption and mitigate climate change.
“Heating accounts for more than half of global energy consumption, so there is no doubt that it plays a huge role in CO2 emissions,” said GEA in a recent statement. “We cannot underestimate the importance of integration and a systems-led approach to dramatically upscaling renewable energy with heat that would otherwise be wasted.”
Using gas for hot water and heating is totally unnecessary, according to Kenneth Hoffmann, Product Manager Heat Pumps, GEA HRT. If a house is kept at a regular temperature between 18 and 21°C (64 and 70°F), there is no need to burn gas at 600°C (1,112°F) to make it comfortable, he said. “Using heat pumps, we can boost the temperature of air brought in from outside to make your home very comfortable without using any gas.”
“If the same concept was applied to a number of houses, it would be a significant step towards reducing our overall emissions; do it on an industrial scale, for entire districts and communities, and you have a game changer,” GEA noted. The combination of heat pumps, district heating systems for domestic and municipal buildings, and natural refrigerants with renewable energy offers the ideal solution for genuinely “green” communal heating, according to the manufacturer.
Although a heat pump runs on electricity, it can generate up to five times more heat energy per kWh usage of primary energy (electricity) than burning gas or using direct electrical boilers.
As electricity is increasingly generated from renewable sources, a heat pump installed today will have a smaller carbon footprint every year until the electricity is from 100% renewable sources. “By combining energy efficiency with burning less gas, we can achieve the decarbonization of society that we desire,” said Hoffmann.
Phasing out coal and other fossil fuels while innovating for the future is an absolute imperative, said GEA. The use of heat pumps in district heating not only helps the global environment but also has local effects as unlike gas boilers, heat pumps do not emit nitrogen oxides (NOx). They, therefore, lead to cleaner air in cities and other urban areas — and also offer financial advantages.
It is important to use a natural refrigerant heat pump to also curb any potential direct emissions relating to the refrigerant. According to a recent interview with Hoffmann at Chillventa, GEA’s natural refrigerant heat pump business in Europe is growing rapidly as decarbonization targets take center stage, taking market share from less efficient f-gas units in industrial applications.
“By combining energy efficiency with burning less gas, we can achieve the decarbonization of society that we desire.”
Kenneth Hoffmann, GEA
Multiple district heating installations
A modern, efficient district heating system, using ammonia-based heat pumps, takes the concept to its best possible conclusion, according to GEA. With a small input of (ideally renewable) electricity, such a solution could generate heat from a wide range of sources, including the air, the ground, a factory, a subway network, or a water treatment plant. This can then be boosted to temperatures of up to 95°C (203°F) to supply heating, hot water or both directly to the neighborhood.
The system works best in areas with a high population density and makes the most economic sense when installed during the initial development of an area or during major infrastructure projects — although this is not a prerequisite.
In Malmö in southern Sweden, for example, there are four GEA 10MW (2,843TR) heat pumps installed next to a sewage treatment plant and a waste incinerator near the harbor. They now provide 8% of the total energy usage of approximately 100,000 homes, saving close to 50,000 tons of CO2e every year.
GEA will shortly be unveiling yet more advancements and has recently secured an order for a 22MW (6,256TR) heat pump in Eastern Europe, which includes a new high-pressure screw compressor.
The huge Marienlyst ice rink in Drammen, Norway, provides a competition-standard skating surface during the winter with a 400m (1,312ft) racing circuit and a full-size soccer field in the summer. The heat extracted when forming the ice is boosted by GEA heat pumps, which are used to supply the local town with heat. When summer comes, the temperature under the pitch is raised and the heat pump operates as a ground source heat pump to provide houses with carbon-neutral hot water.
Meanwhile, in Turku, Finland, GEA has supplied a 10MW (2,843TR) district heating system using the residual heat from a combined heat and power plant. The ammonia heat pumps boost the heat from around 25°C (77°F) up to 85°C (185°F) to supply the city’s 190,000 residents via the domestic heating grid. Again, other than a small addition of electrical power, which is increasingly derived from renewable sources, the heating process is carbon neutral.
In the London Borough of Islington, Bunhill Heat and Power Network uses waste heat from the London Underground — boosted by GEA heat pumps — to supply heating and hot water to around 1,350 homes, a school, and two leisure centers. It has been seen as a major contribution to the Borough’s aim of becoming carbon neutral by 2030.
GEA is making a multimillion-euro investment in new test centers that will come online in 2023. “These will be home to cutting-edge rigs that use natural refrigerants, are 90% automated, can operate 24/7, and are Industry 4.0 ready,” said Hoffmann.
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