Electricity from the sun is sustainable, unlike energy from fossil fuel. Only 0.1% of the land area of the planet is needed to harvest enough sunlight to provide for all the planet’s electrical energy needs.
Payback time for energy and carbon used in manufacture
REhnu has adopted a technology that minimizes environmental impact. Our generators are designed for the minimum of materials used, energy consumed, and carbon released during manufacture. The dish reflectors and their tracking supports, the only components that must be large in order to collect the energy, are made almost entirely of glass and steel. These are common materials made already in huge volume by processes already well developed to conserve energy and to minimize carbon emission. Our design is configured to use as little of these materials as possible, but sufficient to survive extreme winds (90 mph) and hailstorms. While the photovoltaic cells in the receivers do use some environmentally sensitive materials, they do so in tiny quantities compared to conventional PV panels, because they are 1,000 times smaller.
REhnu’s generator units are optimized for minimum mass per kilowatt of peak power output. The specific mass is 160 kg/kW. More than half the mass, including the foundation, is in the steel, about 100 kg per kilowatt of power produced. The payback time for the energy used in making the steel is 5 months, while the CO2 emitted in its manufacture is paid back in 3 months, assuming the electricity produced replaces that from a coal-fired plant. For the next heaviest material, the glass at 40 kg/kW, the total payback time for both energy and CO2 is 2 months. The mass of aluminum is minimized to one tenth that of the steel, by transferring heat mostly by liquid coolant—the payback time for aluminum is thus comparable to that of the steel, despite aluminum manufacture being much more energy intensive.
The energy used and carbon dioxide emitted to make all the materials and to manufacture, transport, and install REhnu’s farms will be paid back in two years. This is less than for most other forms of renewable energy. Since the productive lifetime is projected to be 40 years, the net gain is very significant.