The energy used for heating and domestic hot water in a building is lost. How does then the heat recovery system that recaptures and reuses energy work? What different variants are there and how does the recovery impact on properties?
External heating energy
Property owners purchase or themselves generate energy ( (e.g., from geothermal heat or solar panels). Among other things, this energy is used for heating living areas and hot water in the building, but also for the energy consumption of home appliances. Water generally has a temperature of 4–8 degrees when entering a building. Water that is flushed out into drains has an average temperature of 25 degrees. Thus, the difference between the ingoing and outgoing temperature is energy supplied for heating, e.g. for a shower or boiling potatoes. Similarly, thermal energy exits with the ventilated air in a traditional ventilation system.
This is how heat recovery works
Heat recovery is made possible thanks to the use of heat exchanger technology. The task of a heat exchanger is to transfer heat energy from one medium to another, similar to a radiator that transfers the heat from hot water in pipes to the air in a room. The recovery system for a sewage or ventilation system enables recovery of some of the heat present in the water or air, respectively. The efficiency varies in the systems available on the market, but, depending on which solution is chosen, a building’s need for supplied energy can be significantly reduced.
Benefits of heat recovery
1. Significantly improved control of in-going and out-going energy
When investing in modern heat recovery systems, this also includes control modules, which show data for energy consumption and optimise the capacity. In order to be able to recover as much heat energy as possible, modern systems measure the in-going and out-going flows of energy, thus providing a better overview of the building’s supply and any energy leakage.
2. Reheating the living area and water – with already purchased energy
Energy that has already been purchased can be recovered to reheat flats or hot water. For example, the Evertherm SEW system for efficient recovery of wastewater heat can utilize up to 95% of the heat energy available in the building’s wastewater. This corresponds to 20–35% of the entire energy consumption in a typical multi-residential house. That thermal energy is stored and is allocated to the building based on location of the current demand, which may vary due to weather, time of day or the behaviour of the tenants.
3. Economic benefits – profitable heat recovery
Heat recovery reduces the demand for supplied energy and enables savings on the total energy cost for the building – thereby improving net operating profit. An improved net operating profit, i.e. income from rent minus all costs such as operation, administration and taxes, results in a more favourable cash flow and increased building value.
Increase property value and improve net operating profit with energy recovery.
4. Energy savings are good for the environment
Buildings represent a little more than one fifth of Sweden’s total greenhouse gas emissions and 40% of all energy consumption. By recovering and recirculating the supplied energy for heating and domestic hot water up to 20 times, a building’s climatic impact is reduced and the key numbers are improved for sustainability reports and energy declarations. A national implementation of Evertherm SEW in Sweden’s multi-residential house has a potential to reduce emissions by over 275,000 tonnes of CO₂ equivalents annually.
A new energy study: Sweden can save 3.7 TWh per year
5. Heat recovery to manage energy requirements
High energy performance is a must in order to meet the requirements set by the Swedish Building Regulations (BBR) regarding energy conservation. Recovering energy from wastewater will make it easier to achieve ever more stringent energy requirements – and will also make contributions and financing from authorities and institutes possible, which is an important factor where new construction or renovation is concerned.
