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Solar panels have been with us for many decades, I remember the excitement of owning my first calculator around 30 years ago which was powered by photovoltaic cells.
And yet, in that time, we still have not come to a position where they are common place within our lives.
In a 2015 Gallup poll 79% of the US public said they thought the government should put more emphasis on promoting solar power - a higher result than for any other form of power generation.
The pressure on us both as individuals and societies to wean off our love of fossil fuels is growing stronger all the time and so, in this article, I’ll examine just how far away we are from solar panels being a cheap and efficient alternative to other sources of power in our day to day lives.
The phenomena of converting sunlight to electricity was discovered over 160 years ago but it is only since the mid-1900s that the photovoltaics (PVs) have become been produced in a form that we recognise today.
The New York Times in 1954 predicted that PVs would lead to near-limitless energy being produced by the sun, but even today - 70 years on - there are significant limitations to that being achieved with standard panels.
PVs work by converting ‘sunlight into electricity’ (see the video below for more detail).
More specifically, there are materials that absorb photons of light (from sunlight, for example) and emit an electron as a result. This is called the photoelectric effect.
Gather in the free electrons which have been generated and you can produce electricity.
In traditional solar panels, the material used to produce the photoelectric effect is silicon which has a maximum efficiency (theoretical) of 32%, with the record standing at 26% today and standard operating levels of commercially available cells standing at 16%-20%.
This low efficiency is one of two factors that limit the explosive growth of solar panels, the second is the physical property of silicon.
It is a very brittle material, particularly at the purity required in a standard solar panel. To make it robust enough tt sit on the roof of your house all year around, it needs to be sandwiched between thick and heavy sheets of glass, which adds to the cost, lowers efficiency and makes them harder to install anywhere but large walls and roofs.
That’s a very simplified story of the solar panel, now let’s turn to what needs to happen to have them create all of the energy we need.
To get an understanding of the challenge faced in generating domestic electricity needs from solar energy, we need to start by understanding how much energy they need to generate.
According to the US Energy Information Administration (EIA), the average household in the USA in 2014 used around 11,000kWh, with the extremes being between 15,500kWh in Louisiana and 6,000kWh in Hawaii.
1kWh (kilowatt hour) is the same as 1000 watts of power being used in 1 hour. That’s the equivalent of 20 x 50watt light bulbs shining for one hour, for example.
Using the average number above, to become self-sufficient with solar power, we need to generate around 920kWh of energy per month from solar panels - but what does that mean in practical terms?
The not-particularly-helpful answer to this question is: it depends!
The obvious thing about solar panels is the more sunlight hits them, the more energy they can produce.
Solar panels are purchased based on a measurement of the amount of kW they produce. The table on this page shows the amount of energy a 6kW system can produce in various states across America, from 545kWh per month in Seattle, up to 880kWh in Las Vegas.
If we apply this to the 11,000kWh national average, we can see what we’d have to spend to get ‘free’ energy from the sun.
By way of example, this website takes California and Massachusetts as states with the near average consumption rate of 11,000kWh per year.
To generate 11,000kWh across the whole year, the average house in Masuchusettes will need an 8.8kWh system installed, whereas the same house in California will only need a 7kWh system installing to generate the same amount of electricity, such is the impact of the amount of sun you receive.
One other thing to keep in mind is the space requirement for the panels.
For just a 6kW system, you will need 350 square feet of roof space, which is quite a big roof and out of the question if you only have a small house or live in an apartment.
Pulling all this data together, you can work out how much it will cost for you to become independent of power-generating companies and how long it takes to payback.
In general, it is cheaper to have systems installed in sunnier locations (because you don't need them to be so big) but around $11,000 is going to be enough to purchase a system large enough to meet your energy needs for a year.
If you’re reading this and wondering how they provide power when the sun is not shining, it’s through a battery system which will feed your house when the sun is not doing it directly. The solar panels feed any excess energy produced (such as in the day when you're at work) into the batteries to keep them powered up.
The payback period of solar panels is almost completely dependent on three factors:
If you have more sun and a higher grid energy cost, your payback will be lower than someone who has less sun and lower grid electricity.
You should work on the basis that it will take between 10 and 20 years for an average installation to payback.
The question posed at the start of this article was: How far away are we from solar panels being a cheap alternative to grid electricity?
There are two things that need to happen to get a universal take-up of solar panels:
Perovskite is not actually a material, it is, in fact, the name given the chemical structure of any compound which is similar to the original mineral perovskite.
In PV technology, perovskites are the up-and-coming stars of the efficiency world. They are relatively new and only being produced in the lab at the moment but, as the chart on this page shows, in the few short years since they became widely known in 2012, they are already hitting 20% efficiencies - on a par with the silicon technology of many decades investment.
The reason they are being seen as the next big leap is they are significantly cheaper to produce than traditional silicon cells, which means the payback period at a similar efficiency, is much lower too.
Even with the dramatic progress made to date, perovskite cells are still estimated to be 5-10 years away from commercial production. There are issues such as the robustness of the material and the fact it contains lead in its current guise, but they are not the biggest challenges.
To date, the largest sample of well-made material is only around one square centimetre in size and it looks quite complicated to be able to manufacture larger areas.
It may well be the case that perovskite materials are used to overlay silicon to make more efficient cells (perovskite works with different wavelengths of light than silicon) in a form we recognise today before we create stand-alone perovskite cells.
One additional consumer advantage is this material can be coloured, which has the potential to make it a more desirable product to have mounted on the outside of your home.
With a particularly cool sounding name, this tech also has the potential to transform the PV industry and put solar electricity production in the homes of most Americans.
You may have already heard of quantum dots as they have made their way into tv sets and tablets, but now they are showing huge potential in the solar energy market.
Quantum dots are semiconductors of a minute scale - as small as 50 atoms across - that are able to emit light in response to electricity (which is why they are being used in screens).
They are emit infra-red light in response to being hit by photons from sunlight and this makes them very exciting in the solar energy field.
They are small enough to be embedded in glass and the glass still be see-through.
The infra-red energy light can be guided to a solar panel at the side of the glass pane to create electricity.
Sounds like a lot of effort?
Maybe, but think about this: every window in your home generating electricity!
The latest versions of this technology (which is still only in the lab) contain no toxic metals either, so, in theory, safer for the environment than the perovskites discussed earlier.
Costs of production are still a core issue but progress is also being made on that front. And whilst efficiency is not great, it’s thought to max out at 10% the available surface area is much greater than solar panels on a roof (particularly in commercial buildings) which is why they are so exciting.
There are obviously some exciting developments coming in the future of solar technology.
I’ve outlined the potential for both quantum dots and perovskites, and there are others which this article from MIT covers well.
It also points out that the road to new technology in this arena is long and winding and that there is no single technology that promises to hit the three prime targets of the industry:
You’ve seen that it is possible to become electrically self-sufficient based on solar technology, but you’ll need a really decent roof area, around $12k and to accept that you won’t break even on the deal for at least a decade.
Because of all these, it is going to take a long time before we see the American public getting the support to invest in solar technology that they would like to see.
However, the scientists are marching boldly on with this journey and we can be confident that the options available to our children and grandchildren could well spell an end to electricity production as we know it today: every household will produce their own electricity from the sun.
If you enjoyed reading this and would like me to research and write something similar for your business, then please reach out to me at: Adam@AdamKirkWriter.com