In order for an “emission free” power plant to have a net negative impact on the greenhouse gas emissions of the energy supply it must produce enough emission-less electricity to offset both greenhouse gas emissions that it is directly responsible for (e.g. from concrete used to construct a nuclear power plant) and to offset the greenhouse gas emissions from electricity generated for its construction (e.g. if coal is used to generate electricity while constructing a nuclear power plant).
First, all the individual power plants of a specific type can be viewed as a single aggregate plant or ensemble and can be observed for its ability to mitigate emissions as it grows.
(in hours per year) is the fraction of time the plant is running at full capacity,
, (in units of 1/year, e.g. 10% growth = 0.1/year) it will produce additional capacity at a rate (in GW/year) of After one year, the electricity produced would be The time that the individual power plant takes to pay for itself in terms of energy it needs over its life cycle, or the energy payback time, is given by the principal energy invested (over the entire life cycle),
The principle greenhouse gas emissions emitted in order to provide for the power plant divided by the emissions offset every year must be equal to one over the growth rate of type of power to break even.
In the article “Thermodynamic Limitations to Nuclear Energy Deployment as a Greenhouse Gas Mitigation Technology” the necessary growth rate, r, of the nuclear power industry was calculated to be 10.5%.
This growth rate is very similar to the 10% limit due to energy payback example for the nuclear power industry in the United States calculated in the same article from a life cycle analysis for energy.
These results indicate that any energy policies with the intention of driving down greenhouse gas emissions with deployment of additional nuclear reactors will not be effective unless the nuclear energy industry in the U.S. improves its efficiency.
[2] For the environmental impact of solar power, the energy payback time of a power generating system is the time required to generate as much energy as was consumed during production of the system.
[4] Similarly, the energy return on investment (EROI) is to be considered.