Hundreds of years ago, energy from renewable sources was always used directly. Both hydro and wind power drove machinery through systems of gears, and that was how early factories operated. Factories and mills in many parts of the world were powered by water wheels and wind mills before the nineteenth century brought wood and fossil fuel-fired steam engines and later, electricity.
On and Off the Grid
Today, wind and solar energy are most often used to generate electricity, which is then added to the local grid. The electrical grids are networks of supply and distribution cables that take electricity from where it’s being produced and transport it to where it’s needed. There are line losses associated with the grids, but the percentage of energy lost when electricity is stored in a battery is typically much greater than the energy lost to grid-related inefficiencies. For that reason, even small-scale renewable energy producers who use more power than they produce are usually best off adding electricity to the grid rather than using it onsite.
In spite of its disadvantages, using direct, onsite renewables is a compelling idea. There’s something very attractive about going “off-grid” and running a building or a piece of machinery using an independent source of renewable energy. A hundred years ago, all renewable power was off-grid because the grids did not exist. What’s running on off-grid renewable energy today?
Mechanical Systems Running on Renewable Energy
The most common directly powered renewable energy systems take advantage of solar thermal and geothermal energy. The relatively warm, steady temperature below the Earth’s surface and the radiant heat generated by the sun are both available to everyone. While solar voltaic panels can be used to generate electricity, solar thermal systems, which circulate water through pipes or use heat exchangers to transfer energy from the sun’s rays to the water supply, are widely available. They can be used to pre-heat water for domestic use and for heating systems. Because sunlight varies in intensity and is only available during the day, solar thermal systems need backup power in order to provide hot water on demand.
Geothermal heat pumps are more difficult to install than rooftop solar thermal systems, especially in built-up areas, because they require an underground loop. However, they can provide a consistent source of heat; in the right conditions, they can operate independently, heating buildings and providing domestic hot water without the need for conventional boilers or water heaters. For example, in Iceland and in parts of California, most hot water for heating and domestic use is provided by naturally occurring steam from below ground. This only works in areas with rare geographic characteristics, however. In most places, it would be necessary to drill far deeper than is economically feasible in order to run building mechanical systems without additional power.
Vehicles Running on Solar Power
For decades, engineering students around the world have been challenged to design vehicles that run on renewable energy: the energy of the sun. Races like the World Solar Challenge and the American Solar Challenge give design teams, most associated with universities, the opportunity to design cars that use solar panels to power their engines.
All the academic research and design is starting to pay off. Today, there are several cars in prototype, designed by start-ups as well as large companies like Ford and Toyota, that use solar power. The cars that are closest to marketability use solar energy with petrol, diesel or natural gas backup power.
Renewable Energy and Off-Grid Sites
Many of the devices that are running directly on renewable energy today are in off-grid locations. Agricultural sites all over the world use small wind turbines to meet energy needs, and hydro power is sometimes used to run machinery where flowing water is available. Off-grid industrial operations and residences often use renewable sources of energy along with fossil fuel powered generators.
One of the most exciting renewable energy projects today is the use of solar panels and LEDs bulbs to provide light to poor households in remote areas of Asia and Africa. This allows children to study and adults to read once the day’s work is done. Solar powered lighting combines social and environmental benefits for a winning strategy.
Solar and geothermal heating systems are already among the most efficient small scale renewable energy applications. Solar powered vehicles are an exciting prospect, and they may be close to commercial viability. Off-grid purpose-designed renewable energy powered systems are being developed and put into use. Perhaps in the future, the direct and onsite use of renewable energy will become more common, and more technology will be able to run directly on renewable energy.