Apr 09 2013

Assessing Solar Energy

I’m a big fan of solar energy, and specifically photovoltaics (PV). The earth is bathed in free clean energy, far more than we need to run our civilization, and all we have to do is harvest it. But, of course, it’s not that simple.

There are many ways to calculate the efficiency and effectiveness of PV technology. One way it to calculate its cost-effectiveness compared to other forms of energy. The bottom line for any consumer is this – if you install PV in your residence, what is the total cost of installation and maintenance compared to the cost savings of the energy produced?

You can also think about the energy efficiency of PV – what is the total energy cost of manufacturing, maintaining, and disposing of PV across its lifetime compared to the amount of electricity it generates.

Another way to think about solar energy that I had not previously considered, until a recent study was published on the topic, is the net energy costs and production of the entire PV infrastructure. If you consider the world-wide PV industry, how much energy has it consumed compared to the amount of energy generated by installed PV?

You may be surprised to hear that we are just now (probably) crossing the threshold where solar energy is producing more energy than it consumes.

A study by Dale and Benson and published in Environmental Science and Technology analyzed the energy inputs and outputs of the entire solar industry and concluded that as recently as 2010 solar energy was a net energy consumer. They calculate that there is a 50% chance that in 2012 solar power crossed the line to producing more energy than it consumes. They further conclude that the net energy deficit produced by the solar power industry will be paid off by 2020.

Therefore, we can assess PV technology on an individual, societal, and global scale. If I am deciding whether or not to install PV on my rooftop the factors to consider are this – what do the PV panels cost to purchase, install, operate, and maintain, what is their longevity, are there any rebates or incentives available in my state, how much sunshine does my house get, how much electricity will the PV produce, and how much does my electricity cost? This all calculates to the bottom line – when will my investment likely be paid back in energy cost savings?

We can also take the global view as in the current study, which affects decisions about where and how to create PV infrastructure. Essentially what this means is that we should focus our efforts on promoting PV in those areas where energy efficiency is going to be the greatest. This may not be the same areas where cost effectiveness for individuals is greatest.

For example, a high sunshine state with low cost existing electricity may not be as good for the individual, but is optimal when considering the total infrastructure. Therefore government incentives may need to be higher in those states.

I was unclear on one point from the article – did they consider the energy cost of PV R&D? I wonder how much of a contributor this is. Perhaps it is minor enough to ignore.

In any case, taking the long view R&D is worth the investment. PV technology is improving incrementally every year. I follow science new pretty closely, and I think I can say without exaggeration that hardly a week goes by without a publication about some potential advance in PV technology. Perhaps we won’t have the dramatic sudden breakthrough we would like to have, but slow steady progress adds up over time.

Scientists are developing new materials, new manufacturing techniques, and tweaks to existing techniques that add efficiency, increase durability, ease installation, and lower production costs. While efficiency of conversion of sunlight to electricity is the sexiest feature we look for, the cost (both dollars and energy) of manufacturing is perhaps the most important.

The final question, which I can only touch on in this article, is this – what are the key barriers to expanding the solar infrastructure? I hear two answers – cost effectiveness or political will. The latter is primarily determined by the current cost of electricity production. As long as relatively cheap electricity is available from fossil fuel or other types of energy plants, they will crowd out solar.

Those who believe it is more a matter of political will argue that the current situation is mostly the result of priorities – subsidizing the fossil fuel industry vs investing in solar research and infrastructure. Germany is offered as an example of this, as they have invested heavily in solar power. They currently generate about 3% of their electricity from PV.

Given the rate of technological advance in PVs it seems likely that projections of cost and energy efficiency of PV are going to get significantly better. If we make it a priority, by somewhere between the middle and end of this century we could be living in a solar powered world.


Note – Some of my thoughts above are based on a conversation I had recently with my brother Joe who works in the energy efficiency industry.

34 responses so far

34 thoughts on “Assessing Solar Energy”

  1. lowbatteries says:

    Solar City thinks the math adds up. They’ll install a solar system for you with no initial cost and get their ROI over 20 years worth of monthly payments. (I believe there are other companies doing the same thing).

  2. Neil says:

    As far as the energy cost of PV research is concerned, I don’t think that that component can be very large, because most of the work is done on a small scale (even for people trying to figure out how to produce large-area thin film PVs). And if PV research wasn’t being done, something else would be done in its place by the same people, which makes it, essentially, a net wash. I’m looking forward to the day when my city will let me install white shingles and provide opportunities for solar subsidies that allow me to finance the panels at the same monthly price I’m currently paying for my power.

  3. I agree – once you can pay for the solar panels solely through the saving from your electricity bill, there is no reason not to have them.

    In terms of research, the real cost is lost opportunity. But I think the R&D is definitely worth it given the potential.

  4. petrossa says:

    The Germans surely disagree http://www.spiegel.de/international/germany/german-solar-subsidies-to-remain-high-with-consumers-paying-the-price-a-842595.html as do the British. It’s a lovely pipedream, but sadly only one that’ll work in off the grid sunny places.

  5. Insomniac says:


    I share your enthusiasm, only to a certain extent though. You said that you hear two answers : cost effectiveness and political will. I think there are other answers.

    Photovoltaics have numerous drawbacks, it could hardly be the main energy production technique in our developped countries. I will argue that it should not even be.

    First, it is intermittent. Therefore you still have to store the surplus you produce during the day (the maximum you get is precisely at noon when the need for electricity is at its lowest). Plus you need power during the night, which you don’t have since it’s rather rare to have sunlight at night. You don’t notice this problem nowadays since the photovoltaic installed base in our western countries are ridiculous so the power injected in the grid is negligible compared to what you consume. Note that electricity cannot be stored easily. And progress in this field doesn’t seem to benefit from any big momentum, storage in batteries for example encounters many impediments that make its future look rather dull. You would need (litteraly) tons of batteries in each house that receive its electricity from photovoltaic panels (I can provide the calculation). You would need a major breakthrough in the technology, but it doesn’t seem it would happen in the near future.

    Second, strangely enough it’s not that clean an energy. It all depends on how electricity is produced in the country it’s made. CO2 emissions can vary between 60 and 150 g/KWh (Carbon can be as low as 800, still improving, and nuclear is at 6). Since the main country making panels is China, and that they rely heavily on coal for their electricity production, you realize that it’s not a good idea to buy them panels (the US is actually not that better). That is to say, if you buy panels made in China and use them in France where electricity is mainly nuclear, you’re subsidizing CO2 emission. Unfortunately, public subisidies were handed out to people buying chinese panels in France.

    Then, it’s not economical (for now) but you said it. Its price has been reduced at a good pace but as always, costs decrease quite rapidly at the beggining because there’s plenty of room for improvement. But at the end you have small (tiny ?) improvements making only engineers and scientists happy (I am one of them though). We’re not at this point yet but the question is : for how long will it last ?

    Other points can be discussed, such as the space it would require at the expense of agriculture. Indeed, compared to other sources, it takes huge areas to provide electricity to a town with photovoltaics. Another point is access to materials used to make panels such as rare earth (Who has it ? China, again).

    In comparison, I think that concerning solar power, concentrated solar and thermal solar technologies represent better opportunities than photovolatics to face the great challenge of energy transition. They are cheaper, more efficient and easy to make.

    Let me know what you think, I am opened to discussion.


  6. Insomniac says:

    ERRATUM : Obviously I meant “coal” and not “carbon” in the brackets, at the beggining of the paragraph dealing with CO2 emissions.

  7. tmac57 says:


    Since the main country making panels is China, and that they rely heavily on coal for their electricity production, you realize that it’s not a good idea to buy them panels (the US is actually not that better).

    Let me pose this question to you:
    Assuming China will use their coal produced electricity to produce ‘something’,due to the fact that they are competing in a world market,and need to provide jobs for their people,what then,do you propose that they produce? Children’s toys,cheap electronics,household goods,etc.,or PV panels that may actually offset at least some of the carbon emissions that produced them?

  8. tmac57 says:

    Insomniac- I might also add that your assertion that noon time is the lowest demand time for electricity,is way off by U.S. standards. Noon consumption varies,but is probably at about 70 to 80% of peak demand,and early morning,maybe 4 or 5 AM would be the lowest demand time.

  9. norrisL says:

    I live in Queensland which takes up 1/6th of the Australian land mass. Queensland covers the north-eastern portion of Australia. Queensland is a beautiful place to live. However, it is also the melanoma capital of the world. This is because of the amount of sunshine and the number of white skinned people who, because of our beautiful climate, spend a lot of time in outdoor activities. For example, my brothers and I spent a lot of time playing tennis (my dad was a coach), surfing, fishing (the bay was 150 metres down the hill from our house) and golf.

    This does, however, work out quite well for our 3.6kW photovoltaic array. In our first full 12 months of solar power, we were owed $250 for the year. This comes about because any excess production of kW’s is sold back to the electricity generator. In fact, in our first 3 years of solar power, we did not pay a cent for electricity.

    So, the sun is good because it promotes a great Queensland lifestyle. But ….watch out for that little black spot.

  10. norrisL says:

    in Queensland, the advice is not to buy German panels as they do not work very well here, not sure why that might be other than that they are not made to cope with our amount of sunlight

    In Queensland we sell excess kW’s back to the grid. The kW’s we use overnight cost us 23 cents per kW. The kW’s we sell back the next day nett us 50 cents per kW.

    As I live at 23 degrees south of the equator, we get plenty of sunshine. And even on most cloudy days, we will still produce maybe 40-50% of what we would have done if it was a cloudless day.

    Ultimately, nuclear power is by far the safest and most efficient form of electricity.

    The difference between you and me is that I assume that you are likely living at a higher latitude than I am.

  11. I agree that we will need nuclear for the time being. We should also be focusing on creating next generation nuclear technology.

    The hurdles that insomniac raises are legitimate, but I am not as pessimistic. We don’t need to use farmland for arrays. If every building had photovoltaics that would produce significant electricity, and for centralized production we can use deserts. It would actually not take much to meet our needs.

    Storage is a problem, but not unsolvable. I agree batteries are probably not the way to go, at least for the foreseeable future. Other options include using the electricity to make hydrogen for fuel cells, compressing air in vast underground caverns, or to spin up large fly wheels.

    This will not be an issue for decades, however, until solar capacity exceeds daytime electricity usage. Hopefully in 40-50 years when storage becomes necessary we will have some solutions, and maybe even viable battery technology.

    The carbon issue is also another way to evaluate solar vs other energy options. It is not zero, but it is better than any fossil fuel energy production by far, and only getting better. The technology is such that I think we can rely on fairly predictable incremental improvements over the next 50 years. We are not at the point of diminishing returns. We are just at the point where it is worth installing solar in some locations, and it will only get better from here.

  12. rfhickey says:

    Interesting post and great follow-up points being made all around.

    While I do not wish to stray off-topic here, I guess I will, a little. The production of clean, reliable energy is one pillar of many needed to ensure optimal habitability for life on the planet. When the phrase “cost-effectiveness” has been used in the post and following thread, I cannot help but think of the cost (and carbon) savings that can be captured by energy efficiency improvements, namely those in buildings. McKinsey developed greenhouse gas abatement cost curves which concluded that many energy efficiency improvements have net negative costs, yet many of these are not captured by the market. (See: http://www.mckinsey.com/client_service/sustainability/latest_thinking/greenhouse_gas_abatement_cost_curves). This finding certainly has its detractors who question the assumptions made by the authors, particularly on the point of negative cost which free marketers view as a failure of scientific analysis rather than of the market (See: http://www.brookings.edu/blogs/up-front/posts/2009/12/30-negative-costs-gayer).

    Nevertheless, from the literature on this I have read, while net negative costs may or may not be “real”, significant emissions and energy savings can be realized through very cost effective building refurbishments to existing structures and new building techniques. While all options should be explored and the proper mix of renewable sources, improved traditional sources of energy, CC&S and energy efficiency improvements, I feel that energy efficiency is underrepresented in the sustainability debate and is a low-cost and relatively low-tech place to start for many possible interventions.

  13. Insomniac says:


    Well, you raised the question : “Is it preferrable that Chinese workers produce PV or other stuff, given that PV will partially balance its emissions.” It’s an interesting question, but that is a bit off-topic here. We are discussing western energy policies. Should we subsidize PV or put our money elsewhere ? For one euro spent, how much CO2 have I prevented ? The answer is simple : if there are public incentives to buy PV made in China (or probably elsewhere) while you live in countries in which you have elctricity with low content in CO2 such as France (my case) or Sweden, then the net result is negative. There is no point in doing this in the context of reducing CO2 with public intervention.

    “I might also add that your assertion that noon time is the lowest demand time for electricity,is way off by U.S. standards. Noon consumption varies,but is probably at about 70 to 80% of peak demand,and early morning,maybe 4 or 5 AM would be the lowest demand time.”

    => To me when it’s 4 or 5 AM it’s still the night. I said that noon (or 2 PM) is the moment when you have your peak in PV electricity production, but that it corresponds to a low point in daytime demand. Peaks in demand are in the morning at 8 AM and in the evening probably at 7 or 8 PM. Obviously demand during the night is smaller than during the day. Therefore you have to store it during the day for the next peaks.


    The thing is that the company that produces electricity in your country has to buy your electricity when you have surplus. There are deals saying that it has to, even if it is probably more expensive than its own. In France, there are laws forcing EDF (Electricité de France) to buy your PV electricity even if it’s far more expensive than what you pay for its own (by a factor 2).


    My point was that your last sentence is a rather bold statement. We couldn’t live in a solar powered world in the same way we live now. We would have to (we actually should and probably eventually will) divide or energy consumption per capita by something like 2 or 3. I acknowledge that I addressed a kind of straw man here, with a misrepresented position that we could have all our electricity produced this way. I think it’s clear there is no way we could do that.

    Other techniques could be used to store electricity as you said. They all represent fields of research and we’re making good progress. For example we’ve been using hydroelectric storage by pumping water up and down to release electricity for decades.

  14. ccbowers says:

    “Second, strangely enough it’s not that clean an energy. It all depends on how electricity is produced in the country it’s made. ”

    You are missing the other side of the equation, Insomniac. The comparison must also based upon how electricity is produced in the location the energy is needed. In other words, what would the solar energy be displacing. This question is not just by country, but highly regional. I live in New York State, and as a state we get our electricity from a wide range of sources and only about 10% is from coal, but there are states geographically close (e.g. Ohio, Indiana, West Virginia) that may get 80-90+% of their electricity from coal. I only use that as an example of regional differences, which would change the equation even more when you add weather into the mix.

  15. Part of the point of my article, and the article I was reviewing, is that we should build a solar infrastructure smartly, by starting with the low hanging fruit in terms of energy efficiency. You add another element I should have also mentioned – carbon efficiency.

    So, yes, we probably should not buy solar panels from China to displace nuclear power generated in France. But we should use solar panels in locations where there is lots of sunshine and current electricity generation is not cost, energy, or carbon efficient (relatively speaking). Identify those locations where solar would provide the most bang for the buck all around, and start there.

    In 20 or so years, once we have picked the low hanging fruit, solar will have advanced. At the same time fossil fuel efficiency is decreasing (energy cost vs energy output). Options for mass energy storage will also probably advance in the next 20-50 years – especially if we invest in such technology.

    I don’t know where this will all end. We may need nuclear for a long time to meet our energy needs. We may need other sources of electricity, like wind (although I’m not a fan because of current environmental effects), maybe some biofuels (also not a big fan, but there could be a limited role). Hydroelectric is still a good option. We may put solar collectors in orbit, and solve the daytime production problem. Controlled fusion may be coming on line. 50+ years out we simply cannot predict. But mapping out the next 50 years, I think solar should play a growing role, specifically by charting a path through the most efficient implementation (including carbon).

  16. Fred Cunningham says:

    During the summer months in the US and other countries that use a lot of air conditioning the peak usage is on sunny afternoons and fixed solar panels are orientated to match the peak. This means that the solar output replaces the highest cost peak load generators. This was very effective in Germany last year. Since there can be a savings for all the rate payers, this would justify subsidies to PV users.

    While we may eventually develop more efficient technology for nuclear our, current project looks at this point to be a $14 billion rabbit hole. One problem that we’ve run into with thermo-electricity is during heat waves power plants have had to shut down because of loss cooling ability. When rivers are used for cooling, power plants have to shut down when the river reaches a certain temperature. We have a lot of other things to develop before getting into nuclear. For example a better grid and off shore wind. The lowest hanging fruit is lighting efficiency. Currently we have 450 lumen 6 watt LED bulb for $10 and there is reason to believe that a 950 lumen 10 watt LED bulb will be available in a year or so for the same price.

  17. Bronze Dog says:

    I had big, inflated hopes for solar when I was a kid. It’s good to hear about progress being made, though it’s taking a lot of time. I think it’s taught me to keep my hopes reasonable. Solar isn’t going to be a magic bullet, but it looks to me like it’ll eventually be a useful chunk of energy production, and every bit of green energy will help. Nuclear is probably going to be the best option for the bulk of energy production, though I’m worried about the level of safety regulation versus crony capitalist greed cutting corners, at least in the US.

  18. norrisL says:

    My brother lives in a location where the cost of running electricity from the nearest current power pole to his house would be extraordinary. I do know that in 1990 when he built his first house that it was going to cost him 10 000 Australian dollars to get power from the bottom of his driveway to the house, a distance of 100 metres. Where he currently lives he is 1.6km (1 mile) from the nearest power pole.

    So we multiply $10 000 (cost of 100 metres of power line and pole/s) x 16 (16 x more power poles and line than at his first house) x 2 (a generously small allowance for 23 years of inflation, the cost of running power to his house today would be $320 000.

    I would suspect that the real inflation effect would make the cost more like
    $400-500 000.

    SO, instead, he has a bank of batteries and solar panels. He notes that his current set up is far more efficient than his original set up from 1990, due to improved efficiency of panels and batteries.

    As far as my own arrangement of selling excess solar produced electricity back to the supplier, I am quite aware of the carbon cost of producing and transporting solar panels, but the nett for us was that in our first year on solar, we would have paid $3000 to the government, but instead we had a nett profit of $240. The following year the government raised the cost of electricity. Our electricity production and therefore savings were maintained and the same last year. We have now paid off the cost of solar panel installation.

  19. eiskrystal says:

    I don’t think cost effectiveness is the barrier, it’s actually front-loaded costs that pay back slowly. In our current world with fast political turnover and stretched finances this is an absolute killer to any technology that although useful in it’s place, isn’t the super shiny game changer that was once promised.

  20. elmer mccurdy says:

    You could say similar things about nuclear power plants, yet they keep getting built, like it or not. That’s what the government is for.

  21. elmer mccurdy says:

    Eh, never mind.

  22. ccbowers says:

    “You could say similar things about nuclear power plants, yet they keep getting built, like it or not. That’s what the government is for.”

    I’m not exactly sure what you are implying by this statement, but the building of nuclear power plants has been an issue in the country I live (U.S.), so it is not the exception you imply. The US has 65 nuclear power plants and none have been built in the last 40 years. There are several reasons for this that we can discuss, but it is certainly not the case that they ‘keep getting built.”

  23. elmer mccurdy says:

    Like I said, never mind.

  24. madmidgitz says:

    sbm is down for me does anyone else have this problem

    also it baffles the mind to think that germany is leading the way in solar energy
    while places where 300 days out of a year they have direct sunlight,im looking at you most of australia, they pump money into better ways to burn carbon,more expensive ways to burn carbon and carbon sequestration

    but then again we could pray to the fsm to output more solar power from his holy orbs of meat
    at specific solar stations and get the power companies intrest

  25. madmidgitz says:

    nvr mind i can access sbm again

  26. Kawarthajon says:

    I think that building solar electricity infrastructure on a grand scheme is great, but I have begun to build my own solar panels for dirt cheap (well, not that cheap). The actual solar cells are very cheap ($1.25 each for a 4.1 watt cell). The most expensive part is the glass, which I have been picking up for free from people’s disgarded furniture and windows. Putting the cells together is fun (for me), although it is time consuming. Once you have made the panel, it is good for 20-30 years if you do it right. The other issue is the batteries, which are expensive, but solar power will save me money in the long run.

    We also have a plan in Ontario where you can make money by selling solar generated electricity to the grid. Peak times for electrical use in Ontario are actually during the summer, when air conditioners are working overtime, which coincides nicely with the peak availability of solar electricity.

    I think that there is tons of unused space available for solar energy (whether solar heating, or electricity) on roofs, over parking lots, backyards, etc. While it may not replace all of the electricity used, it can certainly be used for significantly power hungry items that already use batteries, such as electrical cars (i.e. for recharging them while not being used), computers, power tools, lawnmowers, etc… There is definitely a lot more that we could do with solar power than we currently do.

  27. elmer mccurdy says:

    Incidentally, what I meant by “never mind” was, “I realized immediately upon submitting that that was really stupid.”

  28. eiskrystal says:

    such as electrical cars (i.e. for recharging them while not being used)

    A terrible waste of electricity. Change that to buses and electric bikes though and you have my vote.

  29. Bill Openthalt says:


    Anyone who has had to run children to music, ballet or other martial arts classes, or had to buy groceries for a family, and lives in a cold and rainy climate will appreciate the convenience of a personal weatherproof vehicle.

  30. BillyJoe7 says:

    Well, liddle fella, we’d have to go along way back to find something you’ve contributed that could not be so characterised. 😉

  31. elmer mccurdy says:

    Christ, you’re a dick.

  32. eiskrystal says:

    Very convenient, but not the best use of solar generated electricity. I think full sized electric cars will always be a small niche.

  33. Ufo says:

    Steve, have you looked into this yet?


    Palmer, G. (2013) Household Solar Photovoltaics: Supplier of Marginal Abatement, or Primary Source of Low-Emission Power? Sustainability 5(4), 1406-1442; doi: 10.3390/su5041406

    BNC is an excellent site altogether, run by Barry Brook.

  34. Murmur says:

    The viability of solar power has come up quite a bit recently for me. My father-in-law who lives near me is now dusting off his solar water heater as the sun is finally coming out her in Scotland, but as I was discussing this with him he brought up a very good point. I am originally from Zimbabwe and the national grid there is so badly supplied that out of 7 days in a week most people will have 4 or 5 12 hour powercuts.

    It is a way of life and most people have generators to cope with the protracted blackouts. As a country with one of the highest sunlight indexes, the vast majority of people have still not converted to solar power. He was curious as to why this is, and to be perfectly honest, I had very little idea. I suspect cost is a part of it, you can buy a petrol or diesel run generator that will power most appliances including a stove or oven for $500 to $1000, but a decent solar setup costs well into the tens of thousands.

    Just reading about it this weekend I also realised that the payment system there is so badly managed that people have been going for years without paying for their electricity and have therefor put up with the intermittent service as it is better than nothing for free. The interesting thing is going to be when they bring in pre-paid meters in the next few years, people have to pay or get nothing. I always think watching the “emerging” countries is really quite fascinating and the next few years could be interesting in seeing what people who are forced to go without the resources we take for granted come up with.

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