Solar power stands as the world’s fastest-growing renewable source of electricity, and many companies are involved in it, playing a pivotal role in our journey toward a decarbonized future. But how does this incredible energy source work? And what’s the distinction between passive vs active solar energy?
Understanding Solar Energy
Solar energy encompasses light and heat from nuclear fusion reactions inside the sun. The most common modern application involves the photovoltaic effect, where solar power systems capture photons emitted by the sun and convert them into direct current (DC) electricity.
Active Solar Energy: Harnessing Electricity
Active solar energy is what most people envision when they think of solar power. This method involves using solar panels, or photovoltaic modules, to convert sunlight into household electricity. These panels consist of solar cells, usually monocrystalline or polycrystalline silicon, which create an electric field, transforming solar energy into DC electricity. A portable power station or other system converts DC into alternating current (AC) to make this power usable for homes.
Passive Solar Energy: Embracing Heat
Passive solar energy, on the other hand, takes a different approach. It doesn’t rely on solar panels or intricate systems but instead on the intelligent design of homes to utilize sunlight for heating and cooling. Passive solar energy captures and stores heat without mechanical devices by strategically positioning south-facing windows and incorporating thermal mass materials like bricks and tiles.
Delving into Passive Solar Energy
Passive solar energy is a specific type of home design that maximizes sunlight exposure to store heat. Unlike active solar systems, it doesn’t involve solar panels or other balance-of-system components. Here’s how it works:
South-Facing Windows (Aperture)
Unobstructed by shade, strategically positioned windows capture sunlight during daylight hours.
Thermal Mass
Materials like bricks and concrete store the captured solar energy, retaining heat during colder months and aiding in cooling during hotter periods.
Distribution
Natural means, such as radiation, convection, conduction, or additional fans, distribute the stored heat throughout the home.
Sunlight Control
Mechanisms like awnings and blinds regulate the sunlight entering the house.
While passive solar energy alone may not fully heat or cool a home year-round, it can be a cost-effective and eco-friendly solution, especially when combined with additional HVAC systems.
Active Solar Energy Applications Beyond Electricity
Active solar energy isn’t solely about generating electricity but also harnessing heat. Liquid-based active solar heating systems, commonly used for central heating, collect heat through flat-plate collectors. These collectors, distinct from solar panels, capture solar energy as heat, which is then transferred to a liquid, circulated, and used for various heating applications.
Advantages and Disadvantages
Passive Solar Systems
Advantages
Affordable, no solar panels required, zero carbon emissions, noise-free.
Disadvantages
It is not always suitable for existing homes, may require supplementary heating, and relies on available sunlight.
Active Solar Systems
Advantages
Long-term savings, possible government incentives, renewable energy source, easily retrofitted.
Disadvantages
Costly, provides heat but not cooling, may require backup heating, professional installation necessary.
Exploring Active Solar Heating
Active solar heating differs from passive in using additional technology and equipment to capture, store, and circulate heat. Liquid-based active solar heating systems are the most common and typically used to provide central heat. Solar water heaters are another widespread application of active solar power systems, and the principles behind both are similar.
Collecting Heat
Flat-plate collectors may look deceptively like solar panels but don’t use the photovoltaic effect to generate DC. Instead, they collect heat. No solar cells are used, and the construction of flat-plate collectors is quite simple. Often, it’s a large sheet of copper or aluminum painted or chemically treated to be black — enabling it to capture more solar energy as heat.
Heat Transfer
The solar energy captured by flat-plate (or other) collectors is used to heat a liquid — typically water or antifreeze. Once the fluid absorbs enough heat, a circulating pump transfers the hot liquid for either immediate use or storage in the home.
Central Heating and Storage
Suppose the active solar energy collected is used to heat your home immediately. In that case, the hot liquid will be directed to a heat exchanger that converts it into hot air circulated throughout your home using conventional methods like heating ducts and radiators or less traditional means like a radiant floor system.
Active solar energy that’s not immediately required can be stored in hot water tanks or radiant slab systems and accessed when additional heat is needed. Other methods of active solar heating include room air heaters, transpired air collectors, and ventilation preheating.
Advantages and Disadvantages of Active Solar Heating
Advantages:
Potential long-term savings on utility bills in cold climates with adequate peak sun hours
Possible eligibility for government incentives
Clean, renewable energy source
Decades-long lifespan
Active solar heating systems can be configured to heat water as well, providing value in summer months or when central heat is not required
More easily retrofitted to existing homes than passive solar systems
Disadvantages:
Systems can be costly
It only provides heat — not cooling
It may still require a supplementary/backup heating source
Significant building code and permitting restrictions
Requires professional installation
Risk of damage from freezing in extreme cold
Final Thoughts
While solar panels are widely known, passive vs active solar energy systems offer eco-friendly alternatives for heating and cooling. Whether considering a new build or retrofitting an existing home, these systems can provide substantial savings and contribute to a sustainable future. As we navigate the dynamic landscape of renewable energy, both passive and active solar solutions play integral roles in shaping a cleaner, more sustainable tomorrow.
