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Thermal Energy Storage Systems for Energy Efficient Buildings. An integrated solution for residential building energy storage by solar and geothermal resources

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European consortium develops solar and geothermal energy system to heat and cool homes

House builders are promising carbon-free buildings by 2050. A consortium from eight European countries teamed up to develop a smart sustainable system for heating and cooling homes.


Construction companies are promising decarbonisation of buildings by 2050, meaning no CO2 fuels will be emitted into the atmosphere while building or heating those homes. That’s no mean feat. But one European consortium has taken steps to meet that challenge. It has developed a new solar and geothermal energy and cooling system and tested it in three different climates: in hot Cyprus and Spain as well as cooler Austria. The TESSe2b project, coordinated by the Polytechnic Institute of Setúbal in Portugal, demonstrated that the innovative system for homes can cut energy consumption by 80-90 % compared to conventional systems in use. The system uses two types of renewable energy for heating, air conditioning and heating the building’s water and a sophisticated thermal energy storage system. “We use more renewable energy sources and the heating, cooling and domestic hot water production is more efficient than current systems on the market,” says project coordinator Luis Coelho. “TESSe2b reduces energy costs and contributes to decarbonisation.”

Rainy-day storage

The consortium from eight European countries tested improved phase change materials (PCM) for the heating and cooling storage tanks to resolve the frequent mismatch between energy supply and demand, when the sun varies at different times of the day and year. “These materials are used to store latent heat which is generally more efficient than storing sensitive heat,” explains Coelho. The project developed two types of PCM – paraffins and hydrated salts – and developed solutions for the borehole heat exchangers. Those were able to take advantage of the increased underground thermal storage and to maximise the efficiency of the ground-coupled heat pumps. One of the most remarkable aspects of TESSe2b is its control system. It is based on a self-learning algorithm that can be set to different goals: to save net energy consumption; to minimise operating costs; to maximise comfort levels, or to compromise between those goals. “The system learns, by itself, what the best way to operate is under different conditions,” says Coelho. The developers produced compact storage tanks in different combinations to allow the system to be fitted into existing heating, cooling and hot water systems, as well as those in new buildings. The project partners have applied to patent the system and talks are already under way with companies interested in buying it. The demand is there since many European countries and others are committed to becoming carbon-neutral over the next 30 years. Eurostat figures show 75 % of heating and cooling is still generated from fossil fuels while only 19 % is generated from renewable energy and, at the moment, heating and cooling in buildings and industry accounts for half of the EU’s energy consumption, according to ‘Mapping and Analysis of the Current and Future (2020-2030) heating/cooling fuel deployment (fossils/renewables)’. “It’s clear that the market for solutions like ours will increase significantly,” says Coelho.


TESSe2b, carbon-free buildings, decarbonisation, thermal energy storage system, heating, cooling, renewable energy

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