Primer on Solar Energy

Why study solar energy?

By the year 2050, energy needs across the globe will be about twice what we use at present (Figure 1). Dubbed the “energy problem,” this is one of the most pressing challenges facing humanity today.

Figure 1. Historic and projected global energy demand for the period 1980-2030. Data from the U.S. Energy Information Administration

Global development and population growth require unprecedented amounts of energy. In the context of energy security, climate change, and other environmental concerns, it is critical that we undertake a dramatic shift away from fossil fuels. In the search for alternatives, though, we must consider the overall amounts of energy that we can feasibly extract from each. There are many options, but solar energy represents by far the most abundant renewable energy source. It has a potential supply that dwarfs the global demand for energy today and for the foreseeable future (see Figures 2 and 3). However, we need to radically reduce the costs of converting sunlight to usable electricity, heat, or fuel in order to fully realize this potential. We can accomplish this only through the development of new technologies that can be fabricated in massive quantities, are based on plentiful source materials, and are low-cost.

Figure 2. The Sun provides an enormous amount of energy to the Earth.  Lots of things can happen to this energy (absorption, reflection, etc.) as shown here.  Approximately half of the energy actually reaches the Earth’s surface, and it is primarily this energy that is captured for practical use.

Figure 3. Of the vast amount of energy reaching the Earth’s surface from the Sun, this figure provides an approximation of the amount that could readily be harnessed using solar energy technologies.  Assuming land-based systems covering 2% of the available area and converting energy with 12% efficiency (approximately the average performance of current technologies), this amount (67 TW) is more than twice the projected total global energy demand in 2050 (30 TW).  Covering a larger area would push this supply even higher, as would future technological developments that improve efficiency.

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