Don’t panic, but we will need to generate about 15 TW of usable energy from renewable (carbon neutral) sources by 2050 to stabilize CO2 emissions in the atmosphere2 concentration. And purely in terms of available energy, solar energy has the greatest potential to meet this need.
Solar energy is “probably the only long-term energy solution that is both large enough and acceptable enough to meet the long-term needs of the planet,” said Richard Perez, a senior research associate at the Atmospheric Sciences Research Center at SUNY- Albany. Perez’s analysis includes geothermal, wind, all other major renewable resources, nuclear fission, and all forms of fossil fuels.
So while wind, hydro and geothermal energy can work well in certain areas on a local or regional scale, today the potential of solar energy exceeds every other renewable energy source by several orders of magnitude. It is simply the only contender, besides nuclear energy, for a global solution to supply civilization with the enormous amount of energy it needs.
On average, the power of the sun hitting the earth’s surface is 175 W/m2. Assuming that 10 percent of this incident solar energy can be converted into electricity, supplying the energy used by the United States would require covering about two percent of the land in the US with solar cells – that’s roughly the area of North Dakota. Since this is about 30 times our available roof space, supplying electricity from the sun to the grid means building large solar parks.
However, that does not detract from the usefulness of some panels on your roof. If you own your home, you have the option of generating your own electricity. You can reduce or eliminate your dependence on the power company – perhaps even selling back your excess power, further reducing your costs or perhaps even making a profit.
Given the recent change of federal leadership, it is likely a time of great uncertainty for major US solar initiatives. But individual organisations, companies and even citizens can still decide for themselves whether they want to further embrace solar energy. To get a better sense of the current state of residential-scale solar in the United States, Ars looked at the practicalities, the economics, and the experiences of some people who have recently turned their homes into small power plants. Hopefully you’ll find the findings… enlightening, even if you live in a basement.
Better than ever
As a child, many of us have been fascinated by solar-powered calculators and watches. Some of us may have even received science kits with tiny motors attached to palm-sized solar cells. Generating electricity from light seems magical. Why can’t we run the world this way?
One of the major historical obstacles to a solar-powered civilization has been the low efficiency and high cost of photovoltaic (PV) cells – the wafers that convert photons directly into electricity. Their efficiency, or, more formally, photovoltaic conversion efficiencyis the ratio of the electrical power produced by a solar cell to the power of the sunlight falling on its surface.
These actually have a long history. The first solar cell was invented in 1883 by Charles Fritts, who envisioned his solar cells to compete with Thomas Edison’s growing network of coal-fired power plants. However, the efficiency of one percent of its cells made this grand vision an impossible dream.
In 1954, Bell Labs demonstrated a PV panel to the public by connecting it to a toy Ferris wheel and a radio transmitter. This device was six percent efficient, which was a remarkable advancement over previous solar cells. It was also a true ‘panel’, with several individual cells connected together to form a ‘solar battery’. While it was still too expensive for widespread adoption, The New York Times was impressed and proclaimed that it “could mark the beginning of a new era, which would eventually lead to the realization of one of mankind’s most cherished dreams – to harness the sun’s almost limitless energy for of civilization.”
In the 1950s and 1960s, research into silicon solar cells continued. During this period, small cells began to appear in some toy and consumer devices. By the middle of the decade, efficiency had doubled, but costs were still very high, especially compared to the low price of electricity at the time. A one-watt solar cell would cost an early adopter $300, while power plants were built for 50¢ per watt.
By the end of the decade, however, PV cells would prove themselves worthy as an energy source for the then secret embryonic fleet of satellites. The navy, skeptical at first, was then won over
the conventional battery of the first satellite was depleted within days. His solar panel kept him alive year.
The high-performance solar cells used in satellites and spacecraft, while expensive, are responsible
a small fraction of the cost of these systems, and the relatively low cost of fuel and terrestrial power in the 1950s and 1960s created little pressure for lower costs. Nevertheless, solar cells with cheaper materials had been developed in the early 1970s to reduce costs to $20 per watt. This, coupled with the energy crisis that began in 1973, sparked a renewed interest in solar energy for terrestrial purposes.
However, the technology was not yet ready for mass adoption: its efficiency was still close to 10 percent. Moreover, it remained far too expensive.
Today we are experiencing an acceleration of interest in solar energy, both at the residential level and on a larger scale. This is because several factors come together: a significant reduction in costs; increase the efficiency of solar cells; an encouraging regulatory and tax environment; widespread concern about climate change; and major entrepreneurial innovation.
This new wave of interest comes on top of the exponential growth of solar power over the past 20 years. Prospects look good for growth to continue. In at least 30 countries, including parts of the United States, rooftop solar energy is now cheaper than grid energy. not factor in subsidies for solar panels.
Another factor that has aided modern adoption is that many companies are marketing alternatives to the conventional roof panel. Some companies sell more aesthetically pleasing offerings, such as solar cells in the form of roof shingles (the result is a glossy roof instead of one with protruding panels). At least one company offers prefabricated “tiny houses” designed to appeal to different types of customers, including a segment trying to minimize its carbon footprint. Some of those products come with integrated solar roofs and an option to be completely off-grid.
Elon Musk recently claimed that his “sunroof” is cheaper to install than a conventional roof, even without factoring in its ability to generate electricity. Such a reality would make a solar roof a risk-free choice for new construction.
Finally, homeowners are not limited to their roof area. The same installation techniques can be applied to the roofs of carports and other auxiliary structures, and PV panels can even be installed in fields and backyards.
Although we focus on individual residential solar energy, we should mention the growing phenomenon of mid-sized PV installations. These are larger than homes, but still much smaller than utility-sized solar plants. On a recent drive through rural Maryland and Virginia, we occasionally saw a patch of land planted with rows of solar panels instead of filled with cornfields and cow pastures. And in fact, “solar parks” are becoming increasingly popular as a way for communities to reap some of the benefits of solar energy without each individual having to invest in a separate rooftop system.
The sight of them interspersed with crops made an irresistible impression. This is just the latest way to harness the sun’s abundant, free energy, converting it into electrical energy instead of sugar through photosynthesis.