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Our Sole Source of Energy

Paul Kando

In the Sun, two isotopes of hydrogen undergo nuclear fusion, creating helium and releasing a neutron and a large amount of energy, which radiates in all directions.

The sun emits a mid-level flare
photo credit: NASA

When matter absorbs radiation, the energy is converted to heat. The atmosphere’s warmed water and air create the climate in which life can exist. Green leaves of plants absorb solar radiation and use it to power the process of photosynthesis, which converts carbon dioxide from the air and nutrients-laden water from the ground into sugars, releasing oxygen as a byproduct. The sugars and nutrients form and sustain the plants, bodies.

Animals inhale the oxygen and feed on the sugars and the plants. They use the energy and nutrients stored in the plants to power their own metabolism, which ultimately breaks down the sugar molecules to their original constituents. Animals exhale carbon dioxide and release water and nutrients. This is one of many balanced cycles of nature.

Other than our own animal respiration, we derive solar energy from nature in a number of ways: We enjoy the warmth of the sun directly and collect it almost subconsciously through the greenhouse effect of our windows. We can also collect solar heat in fluids (air, water, antifreeze, various heat transfer fluids) and use the heat in our houses or to generate steam for turbine-generators and produce electricity. Wind and hydropower are also derivatives of solar heat. Biofuels — wood, biogas, biodiesel — are solar energy stored in plants recovered by burning.

An increasingly important way to utilize solar energy is converting it to electricity by photovoltaic arrays. PV cells consist of two layers of a semiconductor differently doped to exhibit either a positive or a negative charge when exposed solar radiation. The energized wafers generate direct current, i.e. electrons flowing consistently in one direction. An inverter can then convert the DC current to power grid-compatible alternating current.

Remains of dead organisms are digested by microorganisms, breaking down complex organic molecules into their original, easily recycled components – carbon dioxide, water and nutrients. The exceptions are coal, oil, and natural gas – products of mass extinctions millions of years ago, which buried prehistoric life forms under masses of rock, there to decay under anaerobic conditions. So, fossil fuels are solar energy stored over millions of years in the decay-products of early life forms.

Objectors to solar energy usually invoke economic arguments. However their true objections might be ideological: unlike fossil fuels, solar energy is distributed and available equally to everyone. Why wouldn’t interests used to controlling and profiting from the flow of energy have a problem with this? Science, however, is clear: releasing energy stored over many millennia by burning fossil fuels overheats the planet. Luckily we don’t need to do this: Earth receives 174,000 terawatts (TW) of incoming solar radiation at the upper atmosphere. About half of that, 87,000 TW, reaches Earth's surface. All of humanity needs only 18 TW of energy worldwide. We have plenty of solar power with which to displace fossil fuels, preserving the planet’s climate.