Depending on the generation source of electricity, electricity production can have significant environmental and health impacts. For example, thermal generation sources produce air pollutants that can cause significant harm to human health. The production of electricity can also contribute significantly to global greenhouse gas emissions. Globally, 40% of energy-related carbon dioxide emissions are from electrical generation. Renewable sources of electricity like solar and wind produce zero direct carbon emissions but only generate electricity on an intermittent or variable basis. Hydrocarbon resources like coal and natural gas, although carbon intensive, are the most convenient sources used to generate baseload power to meet consumer demand at any given time.