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Posted 11/24/2017

Let’s talk solar – Powering HVAC systems

Let’s talk solar – Powering HVAC systems

People here are quickly moving towards using energy efficient solutions and green initiatives whether it is for their cars, electronics, businesses or homes. HVAC which stands for Heating, Ventilation and Cooling systems, are also making a lot of progress while being more energy efficient and durable than ever.

Modern heating and cooling systems produce lesser carbon monoxide emissions that help reduce the emission of greenhouse gases into the Earth’s atmosphere. It also means considerable savings on utility costs such as electricity and fuel. Solar panels have been around for a while now, and certainly don’t seem new or unique anymore.

The fact is that solar panels just got a lot cheaper and a lot more practical. Installing solar panels to power your HVAC systems can reduce your power consumption and further bring down your utility bills.

Matters of heating and cooling

The heating and cooling industry is a $266 billion industry. Over 115 million homes in the US consume energy to heat their homes in the winters and cool them in the summers. An estimated 75% of all residential energy consumption in US homes is dedicated to heating and cooling homes and water for cleaning, laundry and baths.

Commercial sector investigation, inspections and environment regulations of 4.8 million buildings is a $50.76 billion sector. Solar energy can dramatically reduce all these figures. As more and more people opt for solar, they are bound to get even better and cheaper.

How does solar integrate with HVAC systems?

For a comfortable home, you need to have the right temperature in all weather conditions. HVAC systems, whether they are built into the central system or individual split units, are capable of providing the most suitable conditions for each part of the house. By harnessing the power of the sun, solar heating and cooling systems convert thermal energy to electricity.

Also known as solar heating and cooling (SHC), thermal energy from the sun is one of the most efficient methods to keep your house a comfortable.

Solar can be utilized in variety of different ways when it comes to heating and cooling solutions.

Solar Air Heating

Solar heaters use a solar collector which has a matrix of copper pipes in it. The rays of the sun heat up these copper pipes and the heat is transferred back into the building via a blower fan. Around 90% of the sun’s heat is converted into reusable energy. The energy can also be stored for times when there is less sunlight and during night.

Solar Water Heating

These generally use water or antifreeze to collect the thermal energy with a heat exchanger but instead of heating the air directly, they heat the water which is converted into steam and distributed across the house. The SEIA estimates that solar water heater sales are approximately around 9 million units per year. Solar water heaters are available in two variants.

Active solar water heaters – use an electric pump to distribute the water within the collector.

Passive solar water heaters – use gravity and thermodynamics to circulate the water within the collector.

Closed loop solar water heaters - These use a heat exchanger with a liquid such as antifreeze, which has a freezing temperature much below that of water. The liquid is passed through the heat collector, and as its temperature increases, is moved to a heat exchanger, where the water is heated. Closed loop solar water heaters are more suitable for colder climates with sub-freezing temperatures. As water expands when it freezes, the pipes can burst. This problem is tackled by using liquids with lower freezing temperatures.  

Open loop solar water heaters – These are simpler systems in which the water directly flows into the solar collector to be heated directly by solar radiation. Solar water heaters based on this design are much easier to construct and maintain.

Solar water heating systems offer various advantages. For one, instead of spending money every month on a gas powered water heater to heat your home, you now have free energy from the sun. According to US Department of Energy (DOE), the average solar water heater can reduce your water heating bills by 80%. By taking fuel out of the equation, you are also protected against future price increases.

Solar cooling

Solar energy can also be used to provide cooling. The American Council for an Energy Efficient Economy estimates around $15 billion is spent every year to keep homes cool in the US. Two types of solar ACs are available today – Hybrid solar ACs, which use photovoltaic panels to generate electricity for powering a regular AC and evaporative coolers which work by evaporating and cooling water.

Hybrid solar AC - These are regular air conditioners that use solar panels with photovoltaic cells feeding DC electricity to them. Hybrid solar air conditioning works by harnessing electricity from the sun via solar panels when the sun is out and switching to a battery backup when it isn't. They can also power the batteries through AC current from the grid directly.

Solar powered evaporative coolers - A solar powered evaporative air conditioner (AKA absorption chillers) operate by evaporating and condensing water. An evaporative solar AC is essentially a large fan with water saturated pads at the front end. As air blows over the pads, it cools down and is distributed into the room.

Both ACs have their respective advantages and disadvantages. While evaporative coolers can decrease the cost of cooling down to nearly zero, they need a regular water supply, which will increase your water bill. Hybrid solar ACs reduce your power bill, however they are far costlier than a regular air conditioner as they need solar panels to work and to install.

Final word

It is worth noting that while solar equipment is more expensive, it pays itself back over the course of time as it reduces the dependence on the grid and power lines. Also, while the cost of a solar air conditioner is high, you can take advantage of the 30% federal tax credit, as well as various state sponsored solar rebates and incentives being offered today.