A combined Organic Rankine Cycle and heat pump integrated with a district heating system

The demand for district heating is expected to decrease in the future, due to competition from heat pumps and energy efficiency measures in buildings. Development of existing district heating systems is therefore necessary for district heating companies to maintain market shares. This Master’s thesis describes and investigates the heat and electricity production and profitability of a combined Organic Rankine Cycle (ORC) and heat pump that is integrated with an existing district heating system. The studied district heating system is utilizing heat from waste incineration. In Sweden waste constitute 20 % of the fuel mix used in district heating systems, and this share is expected to increase in the future. The combined ORC and heat pump operates as a steam turbine system during summer and as a heat pump during winter, with an organic working fluid. Electricity will be produced during summers and heat will be produced during winters. The electricity can be sold and the heat will contribute to the district heating system and accordingly decrease the use of oil. The district heating system of Uppsala is used as a case study. The calculation of profitability is made with the Pay off-method, to give a rough estimate. The result of the thesis shows that the summer case, when electricity is produced, generates 1476 MWh of electricity, and the total revenue from both the electricity and the extra waste fuel will be about 4 MSEK. The winter case, when heat is produced, generates 12 MW of heat, which implies a saving about 33,7 MSEK. The investment cost of the further developed ORC together with other fixed costs is about 30-50 MSEK. The pay off time then becomes 0,8 - 2 years.