The energy supplied for heating and domestic hot water in a property is leaking. But how does the heat recovery technology that can take advantage of and reuse the heat work? What are the different variants and how does recycling affect the properties themselves?
Property owners purchase or have self-produced energy (for example from geothermal heating or solar cells). The energy is used, among other things, for heating living areas and hot water in the building, but also for the energy consumption of appliances. Water generally has a temperature of 4-8 degrees when it enters the property. Water flushed into the drain usually has an average temperature of 25 degrees. The difference between in- and out-temperature is thus energy added for heating, e.g. for a shower or a potato boil. Similarly, heat energy follows out with the air in a traditional ventilation system.
Heat recovery is possible through heat exchanger technology. A heat exchanger's job is to transfer heat energy from one medium to another, like a radiator that transmits the heat from hot water in pipes to the air in a room. Recycling systems for the drain or ventilation system make it possible to recycle some of the heat that is in the water and air respectively. The efficiency varies among the systems on the market, but depending on the solution chosen, the property's need for added energy can be significantly reduced.
An investment in modern heat recovery systems includes control modules, which show data for energy use and optimize capacity. In order to recover as much of the heat energy as possible, modern systems measure inflows and outflows of energy – giving a better view of the property's supply and possible energy leakage.
The energy already purchased can be recycled to reheat apartments or hot water. For example, the Evertherm SEW system for efficient recovery of heat in wastewater can take advantage of up to 95% of the thermal energy available in the property's wastewater. This corresponds to 20-35 % of the total energy consumption of a normal apartment building. That thermal energy is stored and portioned back to the property based on when the need exists, which may depend on the weather, time of day or the behavior of the residents.
Heat recovery reduces the need for energy supplied and saves on the house's total energy cost – something that affects net operating income. An improved net operating income, i.e. income from rent minus all costs such as operations, administration and taxes, provides a more advantageous cash flow and ultimately also an increased property value.
Buildings account for just over a fifth of sweden's greenhouse gas emissions and 40% of all energy use. By recycling and recirculating the supplied energy for heating and domestic hot water up to 20 times, the property reduces the climate impact of the property and improves the key figures for the sustainability report and energy declaration. A national implementation of Evertherm SEW in Sweden's apartment buildings would provide the potential to reduce emissions by just over 275 thousand tons of CO₂ equivalent annually.
High energy performance is a must to meet the requirements of the Swedish National Board of Housing and Urban Development's building regulations (BBR) regarding energy management. Recycling energy from wastewater makes it easier to meet increasingly stringent energy requirements – and also enables grants and funding from authorities and institutes, which are an important factor in new construction or renovation.
If you want to see what a recycling system that uses the energy in the waste water would mean for your energy saving, you can try counting for yourself via our calculator.