What Is The Most Efficient Renewable Energy Source?
There are of course many materials used in each of these instruments, most of them metal, so how much energy is used in the whole process of building them? The Wall Street Journal wrote on a company, Energy Points, that had calculated the energy analysis for the life cycle of renewable sources.
There are many factors that contribute to the score of an energy source beyond energy cost of materials. How much energy can actually be translated into electricity after it is absorbed and how much environmental clearing did it require to set up the units, are two important issues that play a role in the total value of an energy source. This is measured as “Levelized Energy Cost” or LEC, the total energy cost to build and run an energy plant/turbine/etc. over the expected return for the lifespan of the unit.There are many sources of renewable energy, but we’ll compare here the technologies for a solar panel and wind turbine.
More than 90% of solar energy requires photovoltaic cells which are derived from quartz silicon dioxide. The refining of this quartz to metallurgical-grade silicon to polysilicon is energy intensive and can produce toxic compounds, but many manufacturers are harnessing this product to reuse and increase yield of polysilicon. Of course, the reuse of a by-product is usually net-positive although there are energy production costs of this process as well.
While this has been the traditional approach to solar panels, a newer technology- thin-film solar cells- requires less energy to produce given there are inherent risks to this process as well. The thin-film cells are made of cadmium which is a known genotoxin and carcinogen. Beyond the toxicity risks of solar cell production, the energy use in production is usually returned becoming carbon neutral in 2 years or less of use and solar energy retains more than 200% of its original input.
Production of a wind turbine accounts for more than 60% of manufacturing and operating costs of wind energy. The technology demands far less specific refining and processing although the main elements to a wind turbine are steel, copper, and concrete. While being abundant, these materials do require a high production energy cost.
Why are renewables a better source? Well of course, given their name-sake, the energy from wind and solar and hydro turbines is able to be used and reused without requirement of an exhaustible element. Beyond the source is the product after electricity is produced. The waste of coal or natural gas requires environmental mitigation and an excess of energy. Because of this, the total efficiency of usable energy for coal (the least efficient energy source) is just 29% of its original energy value. On the other end of the spectrum, wind provides 1164% of its original energy input.
On a scale of efficiency according to Energy Points, renewables rank solar, nuclear, hydro, geotherm, and wind from least efficient to most, respectively. As these technologies grow and develop, we will hopefully see more demand which will reduce the cost of production and improve the R&D to find more cost and energy effective products. If you see a wind turbine popping up in your backyard, or off your shore, you can know the carbon during its production is many times being offset in less than a year.