Life cycle assessment of ocean thermal energy conversion

Abstract

The use of renewable energy solutions in generating electricity constitutes an interesting option in small island regions. Current energy supply generally comes from fossil fuels and besides high costs this also contributes to high CO2 emissions. Ocean thermal energy conversion (OTEC) is a technology that potentially could be implemented. It makes use of the temperature difference of the ocean to generate electricity. However, an OTEC system has a considerable size. The cold water pipe made of composite is 1,000 meters long and has a diameter of 4 meter. Moreover, the large area required for heat exchange implicates large requirements of (energy intensive) titanium. Therefore it is necessary to investigate the environmental impact of the whole life cycle. This thesis is performed to assess the CO2 emissions associated with OTEC. In order to obtain these results the life cycle assessment method is used. The results for OTEC are compared with diesel, wind and PV technology. Both on a 1 kWh electricity basis and in an energy mix scenario context. It can be concluded that renewable energy impact follows mainly from raw materials, manufacturing and transport, while with diesel the impact is a direct result of the use phase. The CO2 emission resulting from 1 kWh of electricity production by a 10 MW OTEC installation on Curacao is 16 times lower than the CO2 emission resulting from 1 kWh of electricity production by diesel generators. In relation to a 3kW peak PV installation the emissions resulting from OTEC are 1.752 lower. The OTEC emissions are 3.9 times higher compared with an 800 kW wind turbine. In an energy mix scenario this slightly changes in favor of OTEC, even despite the favorable wind conditions on Curacao. This thesis shows that OTEC is a very promising technology considering the relatively low CO2 emissions in combination with base load electricity generation.