Leading Swedish renewable energy pioneer Againity AB and SWEP have joined forces in a pioneering power initiative in the southern Sweden. The initiative has enabled local district heating provider Perstorps District Heating to upgrade its 12 MW biomass-fired heat plant to become a combined heat and power (CHP) plant.
The efficiency of the ORC system
Perstorps District Heating is a joint venture between the E.ON group and Perstorp’s municipality. The upgrade has been achieved by installing an Againity Organic Rankine Cycle (ORC) unit at the Energy Center.
Againity provide a range of ORC turbines and so far have installed 20 units for district heating networks and industrial estates across Scandinavia. Any heat source with a temperature of 90°C and over can be utilized in the system. The source can be heat from a boiler that burns wood chips, landfill gas or household waste, waste heat from a gas engine, hot water from solar panels, or excess heat from an industrial process.
The efficiency of the ORC system is dependent on the temperature difference between the system’s hot and cold side. ORC technology includes a turbine set in motion by the pressure of a vaporized internal working medium. The rotating turbine then drives a generator that produces electricity.
In optimal conditions electrical efficiency up to 20% can be achieved for the largest plants that, for example, utilise waste heat from large gas turbines. If there is a local heat demand, the rest of the energy will be delivered as heat to the local heat network, meaning the total efficiency of available heat source is close to 99,5%.
SWEP brazed plate heat exchangers play an important role in the process. One set of heat exchangers work as the evaporator, meaning enabling the refrigerant to convert from liquid to vapor and another set of heat exchangers operate as the condenser (as such in reverse), condensing vapor to liquid.