In the Faroe Islands, a local company called Defined Energy focuses on recuperation of energy from wastewater. Warm water from showers passes through a heat exchanger, which feeds the reclaimed heat into the boiler.
The cold domestic water flows through the coils, and the hot wastewater flows on top of the coils in the opposite direction of the domestic water, causing it to heat up. Wastewater flows from the top down through the trays to the bottom tray and then further down the drain. The domestic water enters the bottom tray and runs up through the trays to the top tray, after which it is fed into the building. As the hot wastewater migrates down through the trays, it gets colder, because the energy is (taken out and) used for the cold domestic water, which gets warmer for each tray it enters.
The system can be used both in private houses and in public buildings. One example is the swimming hall in Tórshavn. With 165,000 visitors every year, the swimming pool in Torshavn is the largest on the Faroe Islands. In 2013, the annual energy consumption for heating shower water was 327 MWh. By installing four DE-5 heat exchangers from Defined Energy, this was reduced by 58% to 139 MWh per year.
Every year, 3000 TWh are used in Europe for heating water, which is then flushed out as wastewater. This leads to CO2emissions of 600 million metric ton. Defined Energy’s goal is to reduce CO2emissions by creating innovative solutions that secure a better use of energy and at the same time reduce energy expenses.
More information: http://definedenergy.dk/