Hybrid Power

Key points

  • Storing electricity is difficult
  • Solar thermal storage is expensive
  • Hybrid power uses back-up fuel instead
  • Fossil fuels used. Biofuels compete with food
  • Agricultural waste could be used, but low crop yields in best locations for solar
Hybrid Plants

Biofuels and solar electricity

Keeping electricity in one place is a challenge. Batteries are heavy, use toxic materials, begin life inefficient and get worse as they grow older. Yet in the absence of viable alternatives, batteries remain our main domestic storage method, and in an industrial setting, these shortcomings prevent direct storage of our most versatile form of power.

In solar thermal systems, electricity is generated in a steam turbine driven by heat produced in a light collector, which may be stored for back-up generation. Heat is a more convenient proxy to electricity, but even so, high-temperature thermal storage is expensive and potentially dangerous, which significantly increases the cost of solar.

Solar hybrid systems make use of secondary fuel sources as a means to avoid these storage costs. This usually means fossil fuels which are convenient, portable, stable and storable. Hybrid systems are therefore more cost-effective, but are seen as a "quick and dirty" solution.

Biofuel as a fossil substitute has been discounted in the past as biofuel crops compete directly with food production. Food crop residue, often considered an agricultural waste product and burned on site in the field, has recently attracted attention as a potential fuel source but has limited potential in the water-stressed regions best suited to solar.