Using solar energy to heat and cool houses has become popular with American homeowners. One can choose between passive and active solar systems. Both can heat your house with a passive solar system, an ideal choice for cooling it. This article looks at the nitty gritty of these solar systems.
What is a Passive Solar System?
A passive solar system utilizes a building’s material and orientation to collect, store, reflect, and distribute heat in your home. It heats the house during winter and cools it during summer. Passive solar system does not require solar panels and equipment to take advantage of peak sun hours. So, how does the passive solar system work? Let’s find out.
How Does the Passive Solar System Work?
As mentioned, passive solar design uses your home’s material to collect and store solar energy. It primarily utilizes south-facing windows to collect heat and store it in materials known as thermal mass. A well-designed passive solar system can provide ample daylight throughout the year. To have an efficient passive solar system, you’ll need the following:
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South Facing Windows
Also known as aperture, they allow adequate capture of solar energy. The windows should not be obstructed by a shade between 9 am and 3 pm and should face within 30 degrees of true south. The windows should be shaded during cooling seasons (summer, spring, and fall) to avoid overheating your house. And for ample capture of energy, they should remain clean.
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Thermal Mass
Thermal mass (concrete, stone, tiles, and bricks), absorb heat from sunlight during heating seasons and absorb heat from your house during cooling seasons. They do not need to be facing the sun directly to store heat. They have different thermal mass depending on their density, conductivity, and specific heat. Materials with higher density like water store more heat than tiles and concrete. If you live in an area with moderate climate, the drywall and furnishings can be adequate. Just make sure the objects do not obstruct direct sunlight.
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Distribution
Once thermal mass has stored the solar energy, it must be distributed around your house. This is done via any of the following ways: convection, conduction, and radiation. Convection is the transfer of heat through fluids like water and air. Most passive solar systems use convection to evenly distribute heat around the house. Conduction is the transfer of heat through two objects that are in direct contact. Radiation occurs when you stand near a window or a hot object and you feel its warmth. Some homeowners will also incorporate blowers and fans to distribute heat in their houses.
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Sunlight Control
Sunlight control mechanisms dictate how much sunlight enters your house. You don’t want to use clear south facing windows during a cooling season. There are several mechanisms such as roof overhangs, differential thermostats, blinds, and shudders.
Factors to Consider When Using Passive Solar System
Here are aspects to consider when choosing passive solar.
Energy Efficiency
Having an energy efficient home can significantly reduce your heating and cooling bills. Working with companies that design and construct energy efficient homes is a noble step. They can help you use products that bolster passive solar system benefits.
Site Selection
You should select a location where the south facing windows won’t be obstructed by any shade. Fortunately, some residential construction codes require homeowners to offer access to solar. If this is not the case, construct your house on the north end of your property.
Design
For a successful passive solar system, a home designer will consider aspects such as insulation, window location, thermo mass type, glazing type, cooling, and heating systems to come up with a design. There are three designs to choose from: direct gain, indirect gain, and isolated gain.
- Direct Gain
Direct gain occurs when sunlight through the south facing windows hits your walls or floors. They absorb and store the heat, releasing it at night as the room cools. While the use of walls and floors is the most common, it does not store ample heat compared to water. Some homeowners will install water-containers inside the living room to absorb and store heat. It however requires specialized installation and can be expensive.
- Indirect Gain
Designers using indirect gain install the thermal mass between the south facing windows and the living spaces. The most common design is the Trombe wall, which consists of an 8-inch dark wall on the south facing side of your house. A glass is mounted in front of the wall, allowing the dark wall to absorb and store heat from the sun. The wall releases the heat at a slower rate of one inch per hour.
- Isolated Gain (Sunspaces)
Sunspace is the most popular passive solar design, which can be included in new or existing homes. Also referred to as solarium or solar room, it provides auxiliary heat, keeping your house warm. It is also used for growing crops although it should not be confused with greenhouses. You can close them off from your house using windows and doors to control how much heat enters your home.
Advantages of Passive Solar Systems
With passive solar systems, you don’t need solar panels or solar equipment to use solar energy. You just need conventional building materials such as concrete, brick, and tiles. It is also more affordable than active solar systems since you don’t buy any accessories. As you’d expect it is quiet and eco-friendly.
Disadvantages of Passive Solar Systems
Passive solar systems are not ideal for existing houses since the south-facing windows ought to be present. If you want to install a passive solar system, you’ll need to renovate your house, which can be expensive.
Since it relies on radiation, convection, and conduction, it may not heat your home evenly. As such, you may need to install a HVAC system or use a heater. Unfortunately, thermal mass does not store ample heat and releasing it tends to be inefficient.
What is Active Solar Energy?
Unlike passive solar, active solar uses equipment to capture, store, and transfer heat. The core equipment is a solar panel that captures solar energy through the PV cells. You can use solar panels such as the BLUETTI PV420 Solar Panel | 420W It not only allows you to heat your home but also to generate electricity which you can store in power stations like the BLUETTI EP500Pro Solar Power Station | 3,000W 5,120Wh.
Liquid-based active solar systems are the most common heating systems. Other methods include transpired air collectors, air heaters, and ventilation preheating.
Liquid-Based Active Solar
Liquid-based active solar is the most efficient system. It uses liquid collectors to transfer heat around the house. You can use flat-plate collectors, evacuated tubes, or concentrating collectors to store heat. The collector contains a working fluid such as water or antifreeze to absorb solar heat. An integrated controller turns on a circulating pump to move the fluid through the collector.
As the fluid moves rapidly through the collector, its temperature increases to 11 degrees celsius, bolstering its efficiency. The fluid then moves to a heat exchanger or storage tank, heating your house in the process.
Transpired Air Collectors
Transpired air collectors consist of metal plates installed on a building’s south facing wall. The dark and perforated metal plates are installed a few inches before the wall, creating an air space. The plates warm up quickly heating the air space.
Blowers or fans draw the warm air into the building heating it in the process.They are however ideal for large commercial buildings since they can overheat small residential homes.
Room Air Heaters
Room air heaters are installed on the south-facing wall or a roof to heat your rooms. Air collectors can be bought from manufacturers or can be built by homeowners. DIY air collectors are easy and cheap to construct and do not require specialized installation.
The collector consists of an insulated metal frame and a dark metal plate for heat absorption. The hot plate heats the air in the insulated metal. A blower or fan draws the warm air into the room
Advantages of Active Solar Systems
Active solar systems allow you to save on electricity bills since you can use the solar panels to generate electricity. Since you are buying solar panels like the BLUETTI PV350 Solar Panel | 350W and solar accessories , you may qualify for government incentives. Like the passive solar system, it is quiet and provides clean and renewable energy. The best part is it has a longer lifespan, meaning you can use it for decades.
Disadvantages of Active Solar Systems
Installing active solar systems is more expensive than passive systems. Another disadvantage is it can only be used to heat your house and not cool it. Most residential areas might require application for an installation permit. Furthermore, it is not a DIY project, meaning you’ll need a professional to install it.
Final Thoughts: Passive or Active Solar System
Well, a passive solar system is the best choice if you are building a new house. Adding south-facing windows is easier than renovating an existing house. It is also ideal if you are on a budget. Active solar system is your best bet if you want to heat your house for decades. Keep in mind an active solar system can only heat your home.
