From: Chris Peters
Date: March 28, 2013
Re: Renewables: Best of the Best
The rapid evolution of sustainable energy is undeniable. Fueled by a multitude of factors including
technology improvements, environmental concerns, rising oil prices, and international unrest, key
stakeholders are increasingly interested in a sustainable energy future. This memorandum seeks to
explore which sustainable solutions are the best and concludes that there is no one “best of the best”
sustainable sources, but rather a blend of solutions. To do that, it is necessary to first define what
constitutes superior sustainable energy. Our energy has traditionally come from fossil fuels because they
have been abundant, accessible, and cheap. Likewise, a truly viable sustainable energy source will have
to satisfy a diverse constituency of stakeholders, not all of whom are mission-driven toward a clean
environment. We will therefore be examining each source on its accessibility, cost, and environmental
Overview Wind energy is perhaps the simplest form of sustainability to understand: wind-driven
turbines convert mechanical energy into electrical energy for the grid via a generator. We can also harness
wind for a variety of practical tasks such as charging batteries, pumping water, and grinding grain (U.S.
Dept of Energy). To achieve economies of scale and utility-grade energy, large numbers of turbines are
typically concentrated in “wind farms” to provide grid power (U.S. Dept of Energy). The wind industry
has been growing more quickly than any other sustainable source. During 2011, approximately 40 GW of
wind power capacity went online around the globe, which is more than any other renewable source (REN
21, 57). In the United States, 2,900 turbines went up in 2010 andAmerican wind generates enough
energy to power over 10 million homes (NRDC).
Costs The cost of wind power has been dropped 85% in the last 20 years (NRDC) due to over-
capacity among manufacturers, increased competition, increasing scale and greater efficiency (REN 21,
59). In 2010, efficient wind farms had average costs of 7 cents per kilowatt hour (NRDC). According to
the U.S. Energy InformationAgency, the estimated average total system levelized cost for wind farms
entering service in 2017 will be $96 per megawatthour (Exhibit C).
Advantages There are many clear advantages to wind power. It is free, unlimited, and given the
abundant United States land mass, there is plenty of space to capture the wind. Arjun Makhijani of the
Institute for Energy and Environmental Research calculated the wind energy potential in the top 20
contiguous states in 2005to be 10,470 billion kilowatt hours; in that year U.S. electrical generation was
approximately 4,000 billion kilowatt hours. Thus, the potential wind generation that year, excluding
offshore sites, was 261 percent what the U.S. generated (31). Additionally, wind plants are quick to build
– less than a year for a 50 megawatt wind farm (NRDC) – and the energy “payback time” is also quick,
with three to eight months operating to recoup the energy consumed in building and installation (NRDC).
Disadvantages Wind is a variable resource that does not blow all the time in the same area. According to
the IEA, the capacity factor of wind turbines ranges from 20% to 40%, which is lower than for other technologies. Wind turbines can also be considered “visually intrusive” (IEA), which means they are
more desirable in remote areas. However, this can increase the cost of energy transmission. Building
offshore sights mitigates some of these problems, but can also increase the costs of installation and
connection to the power grid.
Overview Solar energy uses the sun to generate electricity in two primary ways. The method most
people think of is through photovoltaic (PV) cells that convert sunlight into electricity. This occurs
through silicon cells which, when hit by sunlight, knock electrons free of their atoms to flow through and
become direct current (DC) electricity (NRDC). Nearly 30 GW of new solar PV came online around the
world in 2011, a 74% increase (REN 21, 47). The other primary solar method is “concentrating solar
power” (CSP), which collects the sun’s heat to generate steam that powers an electric generator (NRDC).
More than 450 MW of CSP came online in 2011, an increase of 35% (REN 21, 47).
Costs Solar energy prices have fallen over the past 20 years, with CSP from a plant costing 10-
14 cents per kilowatt hour. On the PV side, continued innovation throughout the value chain, process
improvements, and development of organic materials is lowering costs by 7-8% each year (REN 21, 50).
According to the U.S. Energy InformationAgency, the estimated average total system levelized cost for
PV plants entering service in 2017 will be $153 per megawatthour (Exhibit C).
Advantages Like with the wind, the sun is a free, unending source of energy. Its capacity is also
practically infinite relative to energy use. According to the Makhijani, assuming 20 percent efficiency
and using one percent of U.S. land area, solar electricity generated by PV cells would exceed total U.S.
energy generation by eight times. While this is hypothetical, the IEAreported in 2011 that by 2060, solar
(PV and CSP) may produce the majority of the world’s electricity (Bloomberg).
Disadvantages The sun, like the wind, is variable and fluctuates by location, weather, and time of day
and year. Another disadvantage is cost, which makes solar “economical today in only some
circumstances” (Makhijani 37). This relates to solar power’s low energy density and the need to transport
it from the remote areas where it is often collected (Journal of the International EnergyAgency, 12).
Overview Geothermal energy involves harnessing heat from the earth’s crust to either generate
steam for generators or for direct heating (NRDC). In 2011, geothermal resources provided an estimated
205 TWh, two thirds of which was for direct heat and the remaining for electricity (REN 21, 40). In the
United States, geothermal energy produced just over 3,000 MW of energy in 2010, or half of one percent
of all electricity used in the country.
Costs According to the NRDC, a new geothermal plant would probably charge $.05 per
kilowatt-hour or slightly more during high demand periods (NRDC). According to the U.S. Energy
InformationAgency, the estimated average total system levelized cost for geothermal plants entering
service in 2017 will be $98 per megawatthour (Exhibit C).
Advantages Unlike solar and wind, geothermal energy is less variable as the earth shows no signs of
cooling down from within. It is also abundant an all regions as, regardless of where you are, if you dig
deep enough you will encounter the heat of the earth’s crust. This will be more of a factor as the same
technology developed to tap fossil fuel deep within the earth i