Our Environment: Part 18 – Solar Energy

We will begin our look at solar energy by explaining there are two forms – passive and active.  In passive solar energy the well insulated building is heated directly from the sun without the need for additional technologies.  In active solar energy the build has solar panels.  These panels have a heat-absorbing fluid which collects solar energy and can use it directly within the house or store it for later use.  Here are some advantages and disadvantages of passive or solar heating.

Advantages	Disadvantages
Energy is free	Need access to the sun 60% of the time
Quick installation	Sun can be blocked by trees and other structures
No CO2 emissions	Need a heat storage system
Very low air and water pollution	High cost
Very low land disturbance	Active systems need maintenance and repairs
	Active collectors can be unattractive

Another problem is that most solar energy designs are designed to heat the buildings, not cool – but there are technologies that can help with this – such as:

1. Block summer sun with window overhangs and awnings.
2. Use a light-colored roof to reflect as much as 80% of the sun’s heat.
3. Suspend reflective insulating foil in the attic to block heat from radiating into the house.
4. Place plastic earth tubes into the ground where the earth is cool year-round. Tiny fans can pipe cool air into the house when needed.
5. Use geothermal heat pumps.

Can solar energy be used for high-temperature heat demands – such heating water and generating steam for electricity?

It can, but there are trade-offs.

Advantages	Disadvantages
Moderate net energy	Low efficiency
Moderate environmental impact	High costs
No CO2 emissions	Needs back up and storage systems
Fast construction (1-2 years)	Needs access to the sun most of the time
	Vulnerable to sabotage
	Land use that could be used for other resources

Solar cells can be used to produce electricity directly.  This electricity can be used directly within the building or stored for later use.  This electricity can be connected to the grid and some countries require power companies to purchase excess electricity produced by homes placed on the grid.  These solar cells have no moving parts, are safe and quiet, require little maintenance, produce no pollution, and last as long as conventional fossil fuel and nuclear energy sources.  There are some issues…

Advantages	Disadvantages
Fairly high net energy yield	Need access to the sun
They work on cloudy days	Need storage and back up systems
Quick installation	High costs
Easily expanded or moved	High land use
No CO2 emissions	DC current must be converted to AC
Low environmental impact
Last 20-40 years

As many already know, Florida Power and Light has already invested in this technology – as has the U.S. military.  In our next article we will look at producing electricity from the water cycle.

References

Miller, G.T., Spoolman, S.E. 2011. Living in the Environment. Brooks/Cole Cengage Learning. Belmont CA. pp. 674.