A major aspect in evaluating the transformation of renewable energy sources into electric energy seems to be the rate of conversion denominated in efficiency. What about the energy return on the investments into theses systems? Running costs and maintenance might change drastically for the same system in different regions and and under different environmental conditions? How could we compare different systems set up in different regions/climates? Performance ratios are only one point of view - are there others?
Exactly, very good question indeed Axel. There is the tendency to use the efficiency to evaluate the performance of a RES, or the cost, but the latter can have great variations along time and across the globe. There are however several other considerations that can be made. As if this technology is able to pay back the energy that was required to its manufacturing/use/end of life phases. This can be expressed by the Energy Payback time (EPBT) parameter which is a good metric to compare and evaluate systems in different regions and climates. It is the ratio between the energy invested and the energy generated in a period of time, thus having the period of time units as the EPBT units.
Thank you Nieves,
a superb first input - and this also slowly drags us into the direction of life-cycle assessment. Obviously, to bring the many aspects involved into formula for better evaluation purposes will be a very interesting task, taken into consideration the stochastic indifferent nature of solar and wind compared to the relatively high reliabilty of sea water movement.
To take the right direction in time could lead to more decentralized energy production and "storage" with needs for "central" grid management and control. This cell-like structure could improve critical infrastructure security, a major issue for all governments, and reduce the risk of big area blackouts in case of a comparable local small failure in energy production or management.
Energy payback time is a big issue, that is often forgotten. If payback is more than a few years. It might not worth the trouble to do the conversion. Also, if you think about distributed electric system, this means that you need very large investment in new power distribution infrastructure. This is not factored in life cycle analysis. However, almost everywhere this is that push the electricity price up, which is a strong indication that a huge amount of resources are diverted into this infrastructure adaptation.
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