New technology allows the coupling of electricity, heating, and cooling in an electrothermal energy storage system.
By Raymond C. Decorvet, MAN ETES Business Development, MAN Energy Solutions Switzerland Ltd.
Illustration above: Visualisation of the new ETES heat-pump, district-heating plant in Esbjerg, Denmark, illustration by Arkitema
To reduce CO₂ emissions, global energy markets are moving away from centralized generation based on fossil fuels and towards renewable energy systems (RES) like wind and photovoltaic. However, renewable energy is not always available when needed, creating instability in the grids due to its fluctuating nature. Efficient and intelligent energy management systems are required to reconcile the growing human demand for power with the fluctuating supply.
Today, the most significant challenge lies in making this growing renewable energy supply usable for the heating and cooling sector. According to the REN21 “Global Status Report”, heating and cooling account for 48% of global energy consumption and 39% of CO2 emissions because renewable sources deliver only 10% of the energy. Therefore, to reduce emissions and decarbonize the whole energy industry, it is crucial to develop solutions that consider all sectors, not just electricity generation.
Connecting electricity, heating and cooling
A new technology links electricity, heating, and cooling and solves two fundamental challenges: It helps balance the grid by absorbing large amounts of surplus or off-peak electricity from renewables and feeding it back into the grid on demand. It integrates multiple sectors by generating, storing, and providing thermal energy for heating and cooling purposes.
The heat (up to 150+°C) can be made available in district heating and for manifold industrial processes, e.g., food and beverage. Typical applications for the cold include cooling data centers or air-conditioning large facilities like airports and shopping malls.
The trigeneration energy management solution allows the conversion of electrical energy into thermal energy in hot water and ice and vice versa. The energy is stored in a series of thermally insulated water tanks. Like a domestic refrigeration unit, in ETES, the closed CO2 cycle sees the working fluid compressed or expanded through turbomachinery to store or extract energy.
Depending on specific demands, energy stored as either heat or cold may be directly distributed or efficiently reconverted back to electrical power as required.
Alongside diverse electricity markets such as peaking power, grid balancing, and time-shifting renewable generation, the system allows additional electricity to be generated if there is excess thermal capacity, for example, within a district heating set up during the summer months.
Sector coupling is put into practice.
By intimately coupling the three discrete energy forms, the technology offers commercial advantages such as economies of scale and reduced capital expenditure. More significantly, the technology means that large cities’ heating, cooling, and electricity requirements can be met using only variable output renewable energy.
The Danish port city of Esbjerg will be the first to deploy the new ETES technology to decarbonise a major part of its heat supply. Local multi-utility company DIN Forsyning has commissioned MAN Energy Solutions to supply a turnkey technology solution for heat generation featuring two ETES heat pump systems.
These will be installed in a new district heating plant based on the operating principle of a heat pump – but on a large, industrial scale. With an overall heating capacity of 50 MW, the plant will supply around 100,000 local inhabitants with approximately 235,000 MWh of heat annually.
The location at the Port of Esbjerg will enable the use of renewable power from nearby wind farms and seawater as a heat source for generating heating energy. The new district heating plant will thus guarantee an emission-free alternative to the city’s current coal-fired power plant, which currently provides approximately half of Esbjerg’s district heating and is scheduled for closure by April 2023. The operational flexibility of the heat pump solution will generate electrical balancing power in the short term and, therefore, maintain balance on the grid.
The key, innovative feature of ETES technology is the use of toxicologically and environmentally safe CO2 (R744) as a refrigerant for the entire system cycle. The CO2-based heat pump plant in Esbjerg will be the largest of its kind ever used in the world.
For further information, please contact: Raymond C. Decorvet, firstname.lastname@example.org