Assessment of waste heat recovery for a power generation system based on Volvo dual fuel engines

The electricity production from distributed renewable energy sources, like wind or solar PV, has considerably increased in last decade. To ensure a wide penetration of these renewable sources is necessary to integrate the fluctuation in the electricity production within the existing power network, even in network with limited transfer capacity between clusters. This work investigates possibilities to integrate the fluctuations of the renewable energy sources with production of electricity with a system based on internal combustion engines of the Dual Fuel (DF) type using synthetic natural gas (SNG), and waste heat recovery (WHR).The system retains high flexibility in the electricity output (i.e. quick regulation), and high efficiency comparable to large electricity plants. The design is based on a set of four medium size DF engines for a total power of around 2MW, and a WHR cycle operated with steam. The results showed an efficiency above 50% in a large range of operation of the engines with a peak above 52%, therefore comparable to gas turbine plants. Two designs of the WHR system were investigated (high pressure and low pressure) to improve heat recovery. The high pressure configuration is considered more suitable due to the lower complexity (single heat exchanger), which can be further exploited to expand the number of engines. The efficiency of the steam turbine/expander is the most critical parameter for the WHR system. However, the results showed that even with low efficiency of steam turbine (ηST 50% - 60%) the total efficiency can reach above 50%, when the engines are operated at high load. A high efficiency steam turbine (ηST 80% - 90%) can rise the total efficiency by 2.5 percentile units