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Solar Energy — Renewable, But Just Needs More Efficiency

Solar Panels (Las Vegas, NV)

SOLAR ENERGY. It’s clean, green and renewable. It just needs some more improvements. Although you can go off-grid with a solar power installation, there are some things that potential buyers would need to know. The good news is that it is becoming a vital source of electricity for homeowners in states where there is plenty of sun (California, Nevada, Arizona). The cons are it has a high initial cost and it is also not energy efficient when compared to the current power grid. This is because solar panels do not convert all of the sunlight it collects into electricity. Before we get into the explanation, let’s discuss the basics of solar power.

To capture the sun’s energy to create solar power, panels are created with arrays of PV cells (photovoltaic cells). The cells are made of semiconducting materials like silicon which release electrons when exposed to sunlight. The electrons are then used to generate DC (direct current) that passes through an inverter that converts it to AC (alternating current). This is what provides electricity to lights, household appliances and electronic devices.

Solar Power is good in some places, but not so much in others, depending on your location. The National Renewable Energy Laboratory made a map showing areas that give the best energy band for solar power. California fortunately is one of those states with a band of 2,000 hours per year compared to the tri-state area (NY,NJ,CT) which has a band of 1,600 hours per year. It means there is more energy potential from sunlight on the west coast, particularly the desert, than to the temperate east coast.

Places on the West Coast like Southern California (Los Angeles) are ideal for solar energy generation because of the climate. The west gets more days of sunshine when compared to the Pacific Northwest, Eastern Seaboard and the Southeast region (Florida).

I am not going over installation costs, like with the Tesla solar roof panels since they have incentives and indicators that figure in to your initial investment. Instead this is how much savings can be made after installation costs. So depending on energy requirements, solar panels can only be installed on a roof that faces towards the south which needs to have a certain amount of space free to allow firefighters access to parts of the roof in case of fire, which in California is a space of 3 feet. That setback allows you to install only over 75% of the roof.

If you want to cover 420 square feet, you need to subtract the setback and you get 315 square feet. Each solar panel is 17.5 square feet so you would need 18 panels for the roof. Each panel produces 0.265 kW so you have a total energy potential of 4.77 kW. Now you take the 2,000 band value (in hours) for California and multiply by 4.77 kW is 9,540 kWh per year.

2,000 hours * 4.77 kW / 1 year = 9,540 kWh/year

Based on inverter efficiency and panel performance the losses from wiring, a typical panel loses 0.78 or 78% efficiency. That means that there is a 78% power lost from heat and other factors e.g. resistance, inverter efficiency, etc. Thus the average panel is only 22% efficient, with 29% being the most efficient existing panels can achieve (as of this writing). So 9,540 kWh less 78% is:

9,540 kWh/year - 7,441.2 kWh/year = 2,098.8 kWh/yearor9,549 kWh/year * 0.22 = 2,098 kWh/year

The typical household (US) spends 12 cents per kWh and consumes 10,399 kWh/year (source US EIA and US Electricity Prices from EIA). To compute the amount of total costs for the average US household:

$0.12/kWh * 10,399 kWh/year = $1,247.88/year

In the example I used for 18 solar panels that generate 4.77 kW at 22% efficiency, home owners can save:

10,399 kWh/year - 2,098.8 kWh/year = 8,300.2 kWh/year$0.12/kWh * 8,300.2 kWh/year = $996.02/year (total cost)$1,247.88/year - $996.02/year = $251.856/year (savings)

We can expect to save $251.856 a year with the solar panel setup example. To totally go off-grid home owners will have to generate enough capacity to meet the average consumption of 10,399 kWh (this is an approximate value as there are different factors that affect energy use among households). This would require installing more solar power panels that could meet that value. It also varies among home owners because not everyone has the same amount of space available to install that many solar panels. One thing for sure though is that it increases costs to implement in order to get more power.

When adding the initial costs of solar panel installations, the return on investment could take up to 8 years (not including any depreciation costs or other hidden costs like maintenance). It seems that it is only a small fraction when it comes to savings for home owners. At this point we are only discussing solar energy for residential or home use. Industrial and business use has different rates and requirements.

The use of solar energy to provide power that can scale commercial levels would require a power storage system. An example of this is a battery. Today, Lithium-Ion batteries are the most commonly used. While solar panels can generate and provide electricity during daylight, at night it is different. Solar power is also affected by cloudy weather when it is overcast. The way continuous power can be provided is by storing the energy generated during the day to a battery. At night or overcast days, the battery can then provide power while it recharges from sunlight during the day.

Renewable energy, like solar, have shown their potential for scaling when paired with a battery system. An example of this is the use of Tesla batteries to provide backup power for South Australia during times of rolling blackouts. The battery system stores energy generated from a wind farm. According to reports, the efficiency of the system has saved the South Australian region $40M in its first year of operation. The Tesla PowerPack batteries can store up to 100 MW and provide 129 MWh of electricity when peak demand arises. The Tesla battery installation saved the South Australian government money for building a new coal power plant. By not having to use coal, more carbon emissions were prevented.

Solar panel installation at the Desert Research Institute (Las Vegas, NV). The LV campus generates 390 kW daily with 1,658 panels. That is a production of 235.2 W per panel. That reduces carbon emission by 1.3M grams of CO2. The overall efficiency is lower based on inverter performance. During the day it can peak at 291 kW between 12 and 4 PM. This installation has been around since 2013 and is already providing 7% of DRI’s power needs off grid.

While California was able to generate excess power from renewables like solar energy, it is not that simple to sell back to the power grid because of certain factors. According to reports, there is more supply than demand when it comes to electricity. The excess power generation is a good sign for home owners and solar power producers, which shows that more energy can be saved from the grid. In California this can be further boosted by a new law passed by the California Energy Commission that mandates solar power installation for new homes effective January 1, 2020. The goal is to cut carbon emissions and move toward fully renewable energy by 2045.

Boosting the efficiency of solar panels is another positive outlook for solar power. Materials like graphene are being developed which allow more light to get through to solar cells. This would increase efficiency to higher levels, allowing solar panels to provide more energy. These types of development, while great for scaling energy efficiency, must also be economical enough and reliable to meet demands.

While solar power is not yet at scale to meeting all energy demands, it does help to reduce the carbon footprint. If more power generated are used for lights, home appliances and electronic devices, it can mean less stress on the power grid. More cleaner and greener power is produced. This does not mean it will immediately replace coal and natural gas. When it comes to more energy intensive appliances and devices used on a commercial and industrial level, the grid is still the practical and more cost effective solution at the moment.

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Vincent Tabora

Vincent Tabora

Editor HD-PRO, DevOps Trusterras (Cybersecurity, Blockchain, Software Development, Engineering, Photography, Technology)