After a summer mostly filled with rain in the Nordic countries, both literally and figuratively, the Green Indicator is back with its August issue. In this issue we will discuss the increasing energy need in the world and its impact on the water requirement, both in terms of quantity and quality. We will also discuss the use of tailored surfaces as catalysts and use the fuel electrode assembly as an example as proposed by researchers at Yale University.

/ Christian Hulteberg

Water vs. Energy

With the energy consumption in the world increasing, other resources are becoming strained as well. There is an ever increasing need in the developing world for clean water, for drinking and irrigation purposes. The choice of energy production will have a significant impact on the amount of water that is required for producing the energy required, also impacting the water available for other applications. The power sources that uses the most water is geothermal energy, consuming about 11 metric tons of water per MWh produced; other highly water intense power sources are hydroelectric (5.5 ton/MWh), solar thermal (4 tons/MWh), nuclear (1.5-2.7 ton/MWh) as well as coal and biomass based electricity production (1.5 ton/MWh). In the other end of the spectrum we have natural gas based production with (0.5 tons/MWh), photovoltaic (0.1 tons/MWh) and wind (0.01 tons/MWh), all according to the US dept of energy.

The majority of the water requirement for thermal cycle plants such as nuclear, coal, natural gas and solar thermal comes with the use of cooling tower make-up. This make-up water can be expensive in areas where water is scarce and alternative supplies such as lake or sea water or indeed gray-water should be considered; however in considering these alternatives, the environmental impacts should also be taken into account. However, the different power sources does not only impact the water quantity required, but also the water quality.

The extraction and production of energy for instance will impact the surrounding environment. In the case of oil and gas exploration, water is used for drilling and fracturing which may impact groundwater quality. The same can be said in the case of the impaired water in oil and gas or the water generated during mining operation; it to can impact groundwater and surface water. Also the production of energy with its emission of NOx, SOx, HC and CO as well as thermal emissions impact surface waters, ecology and lead to acidification. Finally the refining and processing of fuels as well as the transportation and storage of energy will lead to water consumption and impacts in water quality.

It is therefore imperative that the scientific and engineering community both take the water requirement into account, given the local conditions, when constructing or refurbishes a plant; but also continues to do research and development of improving and inventing new methods of water purification.