Solar Energy: Active vs. Passive

March 10, 2009 by  
Filed under Solar Panels

Pursuing a green lifestyle is a hot new trend, and the use of solar energy is becoming more and more popular. If you’ve heard about it on the news and are unfamiliar with the basics of it, this article will explore the difference between the two different types of solar energy systems: passive and active. With more information, you can decide which kind might work for you and your home.

Active solar energy systems require some sort of mechanical device (electrical or fuel-run) to work. Think of the type of solar heating systems used to heat swimming pools. Water is heated passively within the solar panels, but electric pumps are necessary to move the water from the solar panel coils to the pool. Solar electrical systems large enough to be self-contained typically have generators as a backup.

Some solar energy systems that generate electricity use motors in the photovoltaic arrays so that they can track the movement of the sun and maximize exposure. There are also solar electric systems that are not completely energy independent but still have ties with the electric company, either as backup or through net metering. With net metering, electric company power is only used at night and during inclement weather. Excess electricity produced by solar panels in the daytime is credited back by the electric company. Any of these systems are considered active as well.

Passive solar energy technology is completely green and sustainable. These systems require no mechanical device to function, which means no additional utility or fuel expense, and no environmental impact. Because of this, passive systems are often considered to be superior to active systems.

One of the most popular methods of using passive solar energy technology is for heating water. A solar water heating system that is completely passive can heat enough water for bathing and washing. The components comprise a collector tank, which is located on the roof or a wall that faces west or south, and plumbing that utilizes gravity to deliver the water. Solar water heating systems work best in temperate climates where the temperature doesn’t drop low enough to chill the storage tank water.

It’s not out of the question to use a combination of both active and passive systems and reap benefits from both. Any active system that uses an electric motor could add solar cells to generate electricity. Motors for moving photovoltaic arrays could be powered with solar cells. Similarly, electric pumps that transfer water in solar water heating systems such as those for swimming pools, can also run by solar cell. Unfortunately, solar cells don’t work without direct sunlight. External generators are often necessary as backup when there is a long stretch overcast or inclement weather. That’s why systems like these can’t be completely passive, but the use of biodiesel in place of fossil fuels is consistent with green living.

Though passive systems might be considered the best way to use solar energy because they are the most environmentally friendly, active systems have wonderful benefits and are 100% more eco-friendly than traditional heating and electric systems. Both are great alternatives for a green lifestyle.