The Institute for Solid-State Nuclear Physics (Institut für Festkörper-Kernphysik, IFK) Berlin in collaboration with the Nuclear and Medical Physics Group of University of Szczecin finished an extensive survey study regarding the so-called „energy returned on energy invested” (ERoEI) of several types of electricity generating power plants.
The ERoEI is an important parameter that describes the overall efficiency of a power plant. It is the ratio of the the total usable energy produced during the lifetime of a power plant to the total energy demand to build, maintain, and decomission the plant, including energy for providing the fuel (if required). The larger the ERoEI, the more efficient the energy resource.
Many ERoEI studies aim for a single type of power plant. They use slightly different methods to estimate the energy demand and the energy output. This makes it difficult to compare the results. Our study uses a uniform systematics so that all power plants can be compared. All steps of the calculations can be tracked in a transparent manner, down to material data used.
The ERoEI study uses Life Cycle Assessment studies of other publications, updates material data if necessary, and applies uniform mathematical rules to care for a fair treatment of all the investigated power sources, comprising nuclear power, coal power, gas power, solar thermal power, photovoltaics, and wind power.
The main results are as follows:
|Power plant type||ERoEI|
|Pressurized water reactor, 83% centrifuge enrichment||80|
|Pressurized water reactor, 100% centrifuge enrichment||120|
|Black coal, underground mined, no transport||29|
|Brown coal, open-pit mined||31|
|Gas (CCGT) natural gas||28|
|Gas (CCGT) biogas||3,5|
A few power technologies can provide a „usable” energy only with the help of storage systems and/or over-capacities. The study also estimates the influence of those additionally needed plants on the ERoEI. The results are as follows:
|Power plant type||ERoEI with storage and/or reserves||ERoEI w/o storage/reserves|
|Wind energy, 1,5 MW plant, german coast||4||16|
|Solar thermal, desert, Fresnel tubes + water steam medium||8||17|
|Solar thermal, desert, parabol tubes + phenyl compound medium||10||21|
|Photovoltaics, polysilicon, Spain, roof | field||1,7 | 1,2||5,3 | 3,8|
|Photovoltaik, polysilicon, south Germany, roof | field||1,2 | 0,7||3,0 | 2,1|