The Future of the Solar Power Industry

Written By: J.T. Stefan, New Jersey Institute of Technology, Department of Physics
March 9, 2018

In 2016, 65% of the electricity produced in the United States came from the burning of fossil fuels. 52% of this electricity was generated in coal-fired plants, releasing 1.2 billion metric tons of carbon dioxide into the atmosphere. This amounts to nearly two and a half times more greenhouse emissions than natural gas generation, which takes claim to the remaining 48% of fossil fuel electrical generation.These methods are clearly not environmentally viable, and neither are they economically so. The energy sector is subject to the laws of supply and demand as much as, if not more than, any other business sector.

The fuels we rely on so heavily to generate our electricity are not infinite; eventually, coal and natural gas supplies will run dry. Long before this, though, the cost of using these fuels to generate electricity will increase exponentially. The question follows naturally then – what do we do?

The Solar Panel

The science of turning light into electricity, photovoltaics, was first discovered in the mid 1800’s, but it took over 100 years to develop solar cells – the individual units that make up a solar panel. It wasn’t until the 1950’s that solar panels gained traction, and even then they were only able to convert 10% of incoming light into electricity. The cost at this time far outweighed the benefit, and solar panels were used only for experimental government programs and space exploration.
As the years progressed, solar panels became efficient enough to break into the commercial market and today peak efficiency measures between 30-40%. In 2016, solar panel cost (including installation) was rated at around $6 per watt, with the average household consuming 1-3 kilowatts hourly (kWh). Additionally, the cost per Watt of solar power has been decreasing exponentially since the introduction of solar panels, a trend that is expected to continue. The price reduction since 2007 alone has been more than 50%.

Solar power is not without shortcomings though – cloudy days, dust, and even the day-night cycle restrict the timing and efficiency of electricity production. Dust and other debris can be cleaned from the panels on a regular schedule, similar to window-washing of skyscrapers. Cloudy weather and short days decrease the amount of energy that can be collected by panels, since generation is tightly linked to light intensity. Considering we lack the ability to control the weather and hours of sunlight, it’s necessary to find a way to work around these periods of decreased output.

Tesla’s Powerwall

Just as the energy production decreases on cloudy days, the production may exceed demand in sunny weather, especially in the summer months. In an effort to capitalize on the excess generation, local power companies (such as PSE&G) may buy surplus energy. This may seem like a win-win for solar panel owners, but the surplus energy is paid through “energy credits” (measured in kWh) that is deducted off the month’s bill. This may be unappealing for those looking to go off the grid, as it is still necessary to draw from the grid at night.

Tesla’s solution to this problem is the Powerwall, a compact and energy-dense battery that connects to the building’s electrical system. With a usable capacity of 13.5 kWh, the Powerwall can supply electricity well throughout the night and supplement solar panel production on cloudy days. The Powerwall’s modular design allows users to connect multiple units to suit the energy needs of the building.

With a Powerwall/solar panel combination, energy rarely needs to be drawn from the grid. The solar panels provide power during the day, with the surplus energy being stored in the Powerwall for later use. The combination not only allows for disconnection from the grid, but also a supply during outages and storms, making the Powerwall even more useful.

The Tuchman Group’s Proof of Concept

The Tuchman Group installed an array of 39 small solar panels on the roof of its vehicle storage and maintenance facility in early 2014. The purpose of the installation was to reduce the amount of energy drawn from the grid. On average, the system generated 20 kWh per day during winter months and 50-60 kWh per day during the summer months. This far exceeded the building’s demand, and excess energy was sold to PSE&G.

In December of 2016, Tesla announced their production of the Powerwall unit, with plans to begin shipping to customers in January of 2017. Recognizing the Powerwall as a major innovation in the green energy industry, the management of Tuchman Group placed their order for a unit in the beginning months of 2017. After some delays with regulatory committees, the installation of the Powerwall has been scheduled for February 26.

With the installation of the unit, the Group will be able to store surplus electricity to power the building at night, without the need to connect to the grid. The summer months, especially, will be quite exciting. While this time of year generally requires the use of energy-intensive air conditioners, 50 kWh per day is still quite a lot of energy. Assuming 2 kWh usage per hour during the day and 0.5 kWh at night, as well as complete charging of the Powerwall’s 13.5 kWh battery, there will still be a surplus of around 8 kWh that can be sold back to the grid. It may still be necessary to connect to the grid in the winter, but the facility will be able to profit from its electricity production while drawing no power from the grid.

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Looking Towards the Future

The ultimate goal of this proof-of-concept is to prove not only the effectiveness of battery storage, but also its viability as a solution to energy volatility in the national grid. One of the biggest obstacles to implementing large-scale solar power is the grid’s current inability to efficiently store excess power.

The most common method of power storage in the US is through pumped hydroelectric storage (PHS), which accounts for 95% of all power storage. During periods of excess production, electricity is used to pump water from a low reservoir to one at a higher elevation. Once demand exceeds production, water is allowed to drain through a hydro-electric turbine into the lower reservoir, producing electricity in the process. PHS is not the most effective way to store excess energy, though, as the efficiency is between 75-85%. Until recently, this was the most effective way to store surplus energy.

With the advent of the Powerwall, Tesla has driven rechargeable battery efficiency up to 92.5%. While an increase in efficiency of 7-8% may seem negligible, this amounts to a huge difference when taking into consideration the United States’ total power production.

Not only is battery storage more efficient, it is also more responsive to spikes in demand than any other method. PHS takes anywhere from 1 to 5 minutes to reach its peak supply rate, while battery response is nearly instantaneous. This makes battery storage especially useful for areas prone to brownouts. In fact, Tesla was contracted by the Australian government to construct a battery storage facility in the southern part of the country. Since this region of Australia is particularly prone to power shortages, the battery storage was highly needed. When the power supply dropped on December 22, the battery storage was able to supply 16 MW of power within milliseconds.

It is clear that battery storage is finally ready to be adopted in the national grid. Not only is this a viable method for large-scale storage, the Tuchman Group aims to prove that this is also effective on a smaller scale as well. With widespread adoption by businesses and homes, localized power storage will provide energy stability, reductions in electricity bills, and a greener future for everyone.

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