The Disadvantages of Solar Ponds

The sun's enormous thermal energy is captured in a solar pond.
••• Comstock/Comstock/Getty Images

A solar pond is often brought up as an example of a power source that developing countries can easily operate. Solar ponds are cheap to build, requiring only land, pond liner and saltwater. But several important disadvantages to solar ponds may render them unworkable as a useful method of storing the sun's energy.

Solar Pond

A solar pond consists of a large pool filled with saltwater that's covered at the bottom with a reflective lining. The heat from the sun will become trapped in the lowest layer of the water, which contains the highest saline density. In this setup, the heat cannot escape through the top of the pool by means of a convection current, as would happen with fresh water. The trapped heat can be used to do useful work, such as powering a Stirling engine, which operates through compression and expansion of air, or be used directly for heating.

Efficiency Problems

Although solar ponds are simple to construct, they are costly in terms of energy efficiency. The maximum theoretical efficiency of a solar pond is 17 percent, assuming that the hottest saltwater has a temperature of 80 degrees Celsius (176 degrees Fahrenheit) and the coolest water is 20 degrees Celsius (68 degrees Fahrenheit). Compare this to a power plant that can generate heat reaching 800 degrees Celsius (1,472 degrees Fahrenheit) -- the power plant has an efficiency of 73 percent. This means that the solar pond is significantly less heat-efficient than the power plant.

Maintenance

To make use of the stored thermal energy in a solar pool, the hot saltwater at the bottom of the pool must be pumped out. This depletes the amount of water in the pool, so new saltwater must be added to the pool regularly. Furthermore, salt crystals, which can accumulate in the water, must be removed to prevent buildup.

Land Area

Solar ponds require a significant amount of land to function properly. Like solar panel arrays, the ability of solar ponds to capture energy is related to their surface area. If this land could be used for other, more efficient energy sources, a solar pond might be a wasted investment -- one pond in Israel took up 210,000 square meters for an electrical output of 5 megawatts. For comparison, this would power fewer than 5,000 American homes.

Related Articles

The Benefits of Desalination Plants
The Advantages & Disadvantages of OTEC
Negative Effects of Solar Energy
A list of Natural Resources of California
Advantages & Disadvantages of Constructing Dams
A Brief Summary of Solar Energy
Environmental Effects of Solar Energy
What Are the Different Types of Phytoplankton?
Pros & Cons of Desalination Plants
Advantages & Disadvantages of Desalination Plants
Pros and Cons of Algae Biodiesel
Adaptations of Ocean Plants
3 Examples of Solar Collectors
Uses of Renewable Energy Sources
Types of Saltwater Ecosystems
How Does a Solar Still Work?
The Most Common Ocean Plants
Effects of Solar Power Farms on the Environment
What Is the Human Impact on the Freshwater Biome?
Positive Effects of Solar Energy