How To Utilise Photovoltaics To Harness Solar Power

How Photovoltaics Work

While photovoltaics (or solar cells) may be the most commonly cited and recognizable solar technology, they are also the most expensive and at times hardest to utilize for a residential home. However, when it’s a viable option, PV is still a technology that can revolutionize how we use energy in the decades to come.

So far, we’ve discussed other solar systems that basically concentrate solar energy and transfer it to another medium – either water or air. With a photovoltaic cell, things are done electronically. In short, the cell is converting the energy from the sun into electricity using a silicon semiconductor.

It’s the same technology we’ve using for years to power computers, transistors and other electronics, but instead of a man-made power source, we are using the sun directly. When the sun’s light hits the PV cell, some of that light is absorbed by a semiconductor made of silicon (or a similar material). The energy in the semiconductor then breaks loose electrons that can travel as they please inside the device.

Once inside, these electrons are pushed in a particular direction, thus creating a current. Once the current has been generated, you can use contacts located on the PV cell to draw electricity off of it to power your devices.

I’ve just boiled down a very complex subject to about 150 words so you’ll have to bear with me when I say it just works. Entire books, classes and college degrees are based on this subject so if you’re interested in how electricity, silicon or semiconductors work, there are plenty of introductory resources to draw from.

However, the basic idea is that those PV cells can take the sun’s rays and convert them in real time to electricity which we can use to power various devices – from the solar-powered calculator we all thought was amazing in second grade to the space station orbiting the earth with solar panel wings catching as much radiation as possible with each circuit.photovoltaic panel

By Fomanu (Own work) [CC BY-SA 4.0], via Wikimedia Commons

Issues with PV Cells

Since the 1950s, photovoltaic cells have been used by various military, government and commercial outfits, and scientists the world over have tried to determine when this technology would become feasible for residential use. When will we all be able to unplug from the grid and start using solar power only?

The problem, unfortunately, isn’t the sun. The sun’s rays produce 1,000 watts of electricity a day for every square meter of the earth they hit. That’s a lot of juice. The problem is the efficiency of the solar cells, which lose quite a bit of power in the transfer, rendering them fairly weak in terms of electricity generation.

Silicon and other conductive materials are also pretty shiny, which means they shoot all sorts of radiation back out, wasting possible energy sources. Up to 2006, the average solar panel only absorbed 15% of the solar radiation that hit it. The goal is 40%.

Of course, new technologies constantly being developed, and some solar panels have been created that can get efficiencies of 41% or higher. But, the cost is high, which makes it tough for a regular guy or gal like you to take full advantage of the technology.

Tapping into the Sun for Your House

With all that in mind, application of solar panels for your home’s electricity use isn’t necessarily that hard. Once you factor out the cost, you simply need to make sure you have the right angle and direction in which to face your panels.

Ideally, solar panels should be angled upwards and should face south in the Northern Hemisphere or north in the Southern Hemisphere, where the sun will spend most of its time throughout the year. If your home’s roof faces slightly east or west, you can still use the panels, but expect some efficiency loss.

Next, you need to determine how much electricity you use and how much electricity your system can produce. Since it’s impossible to know when the sun will shine, you’ll need to use averages provided by the National Weather Service (in the U.S.), or a related agency in your country. These numbers vary but will give you a baseline from which to work.

You will also need to get your average electrical use from your current power provider. It costs roughly $9 per watt of electricity usage to install a solar system. The more watts you use each day, the more solar cells you’ll need to power your home.

The average home runs on between 100 and 300 watts, but beware – 100 watts of electricity is not very much. If you plan on cutting your electricity use to afford a solar cell system, you’ll want to be realistic about how much you can cut.

Another factor many people don’t realize is that most states have systems in place that will allow you to remain attached to the power grid. In particularly drab months with no sunlight, you can draw as much power as you need, and in bright and sunny months or when you’re on vacation, you can sell power back to the electric or gas company for credit, essentially banking it for later use. You’ll need to check with your local government and power provider to find out if it this is an option for your home.

How To Harness The Power Of The Sun To Provide Hot Water

Heating Installations

For the simplest heating systems – the ones where you add a few pipes and install a solar collector and tank on your roof, you can likely install it on your own without any help. However, the more advanced closed loop systems require a great deal of alteration to your plumbing and may even require special permits; discuss your solar heating plans with a contractor before starting any new project.

For a solar heating installation, you’ll need a variety of parts, depending on what your heating system will be used for.

Solar Collectors

The solar collector will either be a flat panel attached to your main tank or a network of tubes that will run water through to be heated. The actual size of most solar collectors is around 4–8 feet, although some can be as large as 12 feet if you have a particularly large tank.

If you have a lot of cold or rainy weather, you may want to consider evacuated tubes for your collector as they cut down on outside temperature influences – a major factor in the winter. Only the sun’s energy will impact the temperature of the water or coolant in your collector this way.solar heater

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By No machine-readable author provided. David.Monniaux assumed (based on copyright claims). [GFDL, CC-BY-SA-3.0 or CC BY-SA 2.5], via Wikimedia Commons

Storage Tanks

A solar storage tank acts as the transitional device between the collectors and your water heater. If you use a closed loop system, the water will be heated in the storage tank by a series of coiled pipes that come from your collector. If you use an open loop system, the water will be pumped directly to the solar collectors for heating and then returned to the hot water tank to be used.

Water Heater

This isn’t necessary in an open loop system that is completely disconnected from the grid, but it is highly recommended because you never know when you’ll lose the sun or need some extra hot water. A backup hot water heater will remain in service, only producing hot water when your solar tank runs empty or the thermostat drops too low on the current supply. You can link them up so that hot water from you solar collector goes directly to the hot water heater and then back to your household supply.

Water Pumps

You’ll only need a water pump if you opt for an active system that requires the transfer of coolant or water from your solar collector to a separate tank and then to the hot water heater. You’ll rarely have to worry about your pump once as they last for 10–20 years and can be powered by any power source in your home – solar or grid-based.

Heat Exchanger

If you have a closed loop system, you’ll netubular heat exchangered a heat exchanger to transfer heat from the solar collector to your cold water supply. This is usually done by running coolant through a series of pipes and back to a solar tank or the hot water heater. Another alternative is to have a pipe wrapped around another pipe, transferring heat to your fresh water as it is transferred to the faucet or bathroom.

Controls and Valves

A number of controls and valves are needed for different types of installations. These will help to determine where the water is pumped and when the hot water is collected using a thermostat in your hot water tank.

The isolation valve is used to cut off and isolate your solar tank if there is ever problem, such as a leak, contamination or improper heating. This way, you can cut off the solar-heated water while maintaining a direct line to your hot water tank if needed.

Another valve you may want to use if you have an open loop system that doesn’t use pumps or controls is a tempering valve. This will allow you to directly impact how hot the water coming out of your facet is. If your water gets too hot, adjust the tempering valve to add more cold water to the mix and get it right.

How simple ideas lead to scientific discoveries

Simple ideas can lead to scientific discoveries

About Adam Savage’s TED Talk

Mythbusters co-host Adam Savage talks about three people who inspired him to be curious: his dad, a former Earth-science teacher, and physicist Richard Feynman.

About Adam Savage

Adam Savage, is the co-host of MythBusters on the Discovery Channel. Savage has been involved in MythBusters since its creation. His role in the show (that he shares with all the other talent) is to either disprove (“bust”) myths or confirm them through testing and experiments done at different scales.

If the myth is about a one-time occurrence and not about whether or not something can happen at all, it is often deemed “plausible” instead. Savage is also a longtime special-effects artist. He’s worked on films such as Galaxy Quest and the Matrix sequels, as well as Episodes I and II of the Star Wars series.