The feasibility of a commercial osmotic power plant

Abstract

Osmotic power is a form of renewable energy which is currently not used at a commercial scale, but it might have the potential to be exploited in a sustainable manner in the near future. It uses the principle of osmosis, which is known for over a century and is used since recent years for several membrane applications. The salinity gradient between fresh river water and salt sea water, separated by a membrane, causes an osmotic flow which can be converted into electricity by using one of the two types of osmotic power generation, PRO or RED. Interested parties have already concluded, by conducting laboratory studies and operating pilot plants, that osmotic power is a promising source of renewable energy in the future. An energy unit rate of 8 cents/kWh should be possible for a commercial-scaled power plant. However, what is lacking in these studies is the actual design of the osmotic power plant. Scaling up of an osmotic power plant to a commercial scale will have a major impact on the design of the main infrastructure. The question is whether a commercial osmotic power plant is feasible if the capital costs of the main infrastructure are included. Answering this question is the objective of this thesis. The research question is answered by conducting multiple case studies with a varying capacity. By considering the revenues and investments over the lifespan of the power plant, the energy unit rate of each power plant is obtained. The general conclusion is that, with the present technology and knowledge, the energy unit rate deviates too much from a marketable energy unit rate. The high capital costs of the intake and outfall system and pre-treatment facility, and the low power plant efficiency ensure that a commercial osmotic power plant is not economically justified. The commercial exploitation of an osmotic power plant is therefore far from being feasible. However, when a number of expected and recommended developments are considered, the energy unit rate will approach a marketable value. The commercial exploitation of an osmotic power plant could therefore be feasible in the near future. Though, the occurrence of these recommended developments seems to be an utopia. The answer to the research question is therefore that the future commercial exploitation of osmotic power is not feasible.