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Can Household Solar Energy be a Primary Source of Low-Emission Power?

Barry Brook's picture
University of Tasmania
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  • Apr 6, 2013
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Guest Post by Graham Palmer. Graham is an industrial engineer and energy commenter from Melbourne. For another BNC post featuring his work, see Does energy efficiency reduce emissions and peak demand?


Click the above image to download the PDF (full version is free – Open Access)

household solar energyWith declining system costs and assuming a short energy payback period, photovoltaics (PV) should, at face value, be able to make a meaningful contribution to reducing the emission intensity of Australia’s electricity system. But will it? Graham Palmer takes a critical look at this key question. The original peer-reviewed paper is:

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

The energy return on investment (EROI) of solar PV has been the subject of many studies over decades, with some recent studies suggesting an energy payback of less than 2 years. However conventional PV-LCA’s usually focus on ingot/wafer/cell/module/BOS, with the LCA boundary ending at the inverter output.

Further, some researchers argue that upstream energy impacts that are beyond the standard PV-LCA boundaries can make up half of the energy impacts.

My paper builds on a recent study by Prieto and Hall titled “Spain’s Photovoltaic Revolution: The Energy Return on Investment”.

Hall is arguably the world’s leading expert on the concept of EROI and Prieto was a chief engineer for several major photovoltaic projects in Spain. Based on real-world experience in Spain’s large PV expansion before the GFC, they conclude that the EROI of PV is far lower than commonly assumed, and may be too low to support an energy and economic transition away from fossil fuels. Given Spain’s excellent solar insolation, this is a serious concern.

Taking a similar approach, I examine the role of high-penetration household PV within the Australian NEM, with a focus on Melbourne. I also include an analysis of intermittency, grid integration and the energy costs of storage. Once these downstream energy costs are included, and assuming that PV has an integral role in the electricity system, the EROI drops below the minimum threshold generally considered necessary to transition from fossil fuels.

I conclude that in a grid dominated by unsequestered coal and gas, and treating PV as a non-essential add-on to an electricity meter, PV provides a legitimate source of emission abatement with high, but declining costs. But at high grid penetration, the economic and energy costs of accommodating PV erodes much of the benefits.

PV’s greatest strength lies in being embedded within the low voltage distribution network as a supplementary power source, where it can potentially provide valuable network support, but will require electricity market reform along with a substantial decline in lifetime battery costs. The conclusion is that the short-run tactical response of the expansion of PV without storage works against a long-run strategic approach to deep emission cuts, which will ultimately require the successful adoption of one or more of the candidate low-emission baseload technologies.

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I K's picture
I K on Apr 6, 2013

PV can not do more than about 10% of a nations needs, 20% if you are lucky to live in a very sunny climate and have demand profile favouring solar output profile.

Storage isn’t possible at the scale needed. Fossil fuels provide chemical storage for “free” so anyone suggesting a storage solution which uses a less powerful storage energy (batteries, gravity, kinetic, potential, pressure, heat etc) is not only proposing a system that needs to be magnitudes of order larger in size but also infinitely more expensive than “free” fossil fuel chemical bond storage.

The only way to achieve solar output exceeding 50% for a nation is to have a global grid. Since the sun always shines onto the earth a global grid can give you near constant output.

James Van Damme's picture
James Van Damme on Apr 7, 2013

“can not”,  “isn’t possible” are absolutes which are not warranted. If you come to a conclusion based on engineering parameters which are variable, you can come to a different conclusion after an improvement in those variables. Perhaps some Monte Carlo analysis would show a way forward?

A global grid? Interesting, but how would you move energy around the globe? Oh yeah, we do that already with oil.

Schalk Cloete's picture
Schalk Cloete on Apr 7, 2013

This EROI analysis just confirms the role of renewable energy as a pathway towards long-term energy security and nothing but a very marginal CO2 abatement option in the medium term. Decades of R&D will be required to get the overall energy costs of renewable sources down to a level where a complex society can be supported by a predominantly renewable energy sector. The solar PV EROI of 2 calculated in this paper will not support even the most basic of civilizations and does not even include the massive additional energy costs assosiated with seasonal balancing. 

In the meantime, the trick is to focus on the lowest-cost and most practical CO2 abatement options so that we can keep the climate system in tact for future generations so that they at least have a fair shot at completing the great transition away from fossil fuels. The focus should therefore be on conservation (lifestyle changes) & efficiency on the demand side and CCS & nuclear on the supply side.

A continued rollout of wind and solar beyond 10-20% of power capacity or in places with only marginal wind/solar resources (i.e. Germany) is a massive waste of precious time and planetary resources. Yes, renewables should remain a high basic research priority, but a large-scale rollout is senseless before the energy costs of balancing are massively reduced. 

It is painful to say this, but, in my humble opinion at least, renewable energy advocates are currently doing more harm than good to the long-term sustainability of human civilization. The fight against climate change is difficult enough as it is. Insisting on using the most expensive and impractical weapons possible just makes no sense.  

Nathan Wilson's picture
Nathan Wilson on Apr 7, 2013

Palmer’s 37 page paper covers a wide range of PV issues, and reveals many negatives for residential PV.  However, most of the issues can be overcome by utility scale solar, at least at low penetration.

For example, a utility scale solar energy system with 5 hours of storage, which was sized to provide 5-10% of peak load, and distributed across a desert, could be just as “grid friendly” as any other type of generation.  It could be made to provide fast ramping, frequency regulation, grid stabilization, VAR support, and black-start like a thermal generator.  Unlike residential solar, it is on the same side of the distribution network as the other generators, so it does not push the line voltage out of spec.

At today’s battery prices, a 5 hour storage system costs about $1.3/Watt using lead acid batteries.  It is plausible that high temperature liquid metal batteries (including NGK’s sodium-sulfur battery and Ambri liquid electrode/liquid electrolyte battery) could reduce the cost enough to be competitive with fossil fuel backup ($1/Watt).  The long life of liquid metal batteries also improves the EROI of the system (compared to lead-acid).  Batteries can share a power inverter with the PV array, improving efficiency and saving cost.

Using a small amount of storage to improve the quality of PV power is different than using large amounts of storage to make solar baseload, at high penetration.  A fundamental cost limitation is that the energy released from storage is about double the cost of the energy that went into it.  Furthermore, at large penetration, the solar generation requires near 100% dispatchable backup (since large storms can turn-off the entire system at once), whereas at low penetration solar requires only the same 15% backup as other systems (where a failure can disable a single generator or transmission line).

This is a much more modest solar vision than most renewable advocates share, but it is fully compatible with existing large-scale non-fossil energy sources (hydro, geothermal, nuclear).

I K's picture
I K on Apr 7, 2013

About ten years ago I had an idea of a passive solar light collector connected to a fibre optic (imagine a football sized snow globe cut in half sitting on the ground, the focal point at the centre where the light is focused into a fibre). You can carry a lot of light energy in a fibre these days (you can make fibre lasers which can cut through a couple of inches of steel). Any passive collector would be very cheap its just glass/plastic.

Anyway, imagine instead of PV collecting at about 15% efficiency and require quite expensive DC to AC equipment you instead feed solar light into a large cavern.

Let the light heat this area to around 700 centigrade, so you have a huge high temperature thermal mass. Pour water down and out comes high pressure steam, like geothermal but at much higher temperatures. You can then convert this to electricity at ~ 40% efficiency and importantly you can run it 24/7

Cheaper than PV
Higher efficiency
Can provide 24/7 base load and even offer ramping up and down like a normal coal plant.
All you need is cheap glass/plastic and a large solid rock cavern.

Wonder if it would work.

Nathan Wilson's picture
Nathan Wilson on Apr 7, 2013

Palmer argues that future battery and smart-grid technologies could bring many of these features to residential solar.  Of course this is possible, but it strikes me as unlikely.  Solar panels are sexy, but a home battery that is controlled by the utility, sometimes releases hazardous gas, and occasionally catches fire, is not.

I K's picture
I K on Apr 7, 2013

The idea of storage is doomed to fail because there are only a few methods to store energy.

Gravity: Expensive and massive
Kinetic: Much more expensive and massive
Pressure: Much much more expensive and massive
Heat: Low grade and expensive
Chemical: Free and high density storage
Atomic: Free and even higher density storage

So we now have ‘free’ chemical bond energy storage, how can anything compete with that?

There is no future technology or advancement which will make gravity stronger than chemical bonds, or pressure store more energy than chemical bonds or make low grade heat more useful than chemical bonds…… especially at the same price of free.

So yes, I can use absolutes because I’m absolutely sure gravity isn’t going to become stronger than chemical bonds in our lifetime nor is any alternative going to become cheaper than free.

A global grid is not that difficult physically or even cost wise, politically its probably not likely anytime soon

Nathan Wilson's picture
Nathan Wilson on Apr 7, 2013

Why would this be any cheaper than concentrated solar power?  CSP is currently more expensive than PV, and direct steam generation is the cheapest CSP.  I would think you’d need, not just passive collection, but active tracking as with CSP.  

I don’ t know about high power fibers, but I think the system would need very specific rock conditions to work; lots of rock formations have cracks or pores that would let your steam escape.  Others would release chemicals that would corrode your equipment.

Also, for energy efficiency, the energy storage volume would need to be very large (so the volume to surface area ratio was high), but solar energy is difuse, which goes the other direction.

I K's picture
I K on Apr 7, 2013

Here is a quick sketcup so you have an idea, each unit due to its shape will concentrate solar light to its focal point where a fibre will carry the light. You can chain as many as you wish, 10, 100, or even millions.

http://s8.postimg.org/4mwgqwi6t/Passive_collector.png

Use the fibre to directly feed a steam boiler just as coal is used to feed a coal power station boiler. Directly feeding a steam boiler would yield efficiencies upto 45% which is much higher than PV, of course you cant use diffuse light it has to be a clear sky.

Or use the light to heat a rock formation to a high temperature so you can use the energy later
Earth itself would act as your insulator. For arguments sake imagine a very large bolder buried in the ground, its mass is very high vs surface area so the energy loss will be low.

You could also use these fibres to heat a homes water storage tank instead of gas or electricity. Or even use a single unit to feed the fibre into your home for lighting

Due to its shape it does not need to track the sun and because it can be made from glass or plastic it would be dirt cheap. It doesn’t have to be a sold glass block you could potentially fill it with water or just have the correct shape on the outer and inner surface like a frenzel lens to give you the correct focal point.

The main advantage is that each unit would cost pennies. Perhaps as low as 10 cents each.
So a m2 of them could be perhaps made for less than $4 and provide you with 1KWp of light energy. That means a one off $4 investment gets you 200watts of average light energy for hundreds of years (passive nothing to go wrong so will last hundreds of years). By comparison $4 of natural gas only gets you the same 200 watts for a week.

Very basic idea, just concentrate sunlight into a fibre. Once you have concentrated solar in a fibre you can do lots and lots of things. Imagine 100 of these feeding 4KW into your homes boiler to meet your heating needs. Imagine 10,000,000 feeding light directly into a 400MW super critical steam boiler to generate eletricity. Or imagine a billion of them feeding 40GW into the centre of a mountain to store heat for winter use or “geothermal electricity generation”

I K's picture
I K on Apr 7, 2013

http://s8.postimg.org/4mwgqwi6t/Passive_collector.png

Because its made of very cheap plastic, has no moving parts, can be placed on the ground with no supporting structure and would last a thousand years and because you can feed a huge number directly into a large boiler or into a rock formation. And importantly it is fully scaleable, from 1 unit to 1 billion units.

Vs expensive complicated solar trackers with small sterling engines on them, or those light towers in spain which need huge towers constructed and lots of expensive sun tracking mirrors.

Stephen Nielsen's picture
Stephen Nielsen on Apr 7, 2013

What if solar used chemical storage (artificial photosynthesis, biofuels, nano-material catalysts etc)? Is this not possible? 

What do you think about the promise of graphene as an energy storage medium on a non-utility scale?  Or do you believe that most if not all energy needs can not bet met on a non-utility scale?

James Van Damme's picture
James Van Damme on Apr 8, 2013

In my state (NY) there are two pumped hydro storage facilities. I presume they did the math and figured that storing water was cheaper than oil fired peaking units. There are lots of others.

The only storage I have at my house (so far) is heat for my solar DHW system. Works for me, and beats using more gas.

There’s talk of a DC grid from Africa to Europe, but the costs aren’t favorable yet.

I K's picture
I K on Apr 8, 2013

Peaking hydro is not storage it is, as the name suggests,  for peaking power. (and sometimes black starts and surges)

 

The uk has a large pumped storage site called Dinorwig. It’s  capacity is only 9GWh which is only enough for about 10 minutes of peak electricity demand so you would need ththousands of them which is fantasy

 

Storage is simply not practical or affordable vs free fossil fuel chemical bond storage.  The only way wind and especially solar can take large market share is with a global grid. Wind and solar advocates mostly don’t understand this. 

I K's picture
I K on Apr 8, 2013

You can store lots of other chemical energy like wood or bio oil but few people would consider generating many terra watts from bio energy sane.  nor is it particular clean or environmentally friendly. 

 

Energy storage is simple basic physics and even more basic economic.

 

Coal gas and oil provide energy for a (relatively cheap) price and the storage of this energy is effectively free. ie the chemical bonds

No other storage medium comes close to the density and free storage of chemical bonds apart from nuclear. 

 

Batteries (ie different chemical storage) of any type will fail for utility scale storage because you can not make them more energy storage dense nor can you. make them cost competitive with free

 

As already noted any other method needs to MASSIVAE because things like gravity are far far weaker than chemical bonds

 

 

Stephen Nielsen's picture
Stephen Nielsen on Apr 8, 2013

Did you hear about the major breakthrough made at Virginia Tech annouced this week? 

 

http://tinyurl.com/cdrbrsy


…It’s seeming less and less impossible every day

Nathan Wilson's picture
Nathan Wilson on Apr 9, 2013

A new process to make hydrogen from biomass?  I would not call it a major breakthrough.  We already know how to make bio-methane, bio-methanol, and bio-ammonia; any one of which is more suited to low cost cars (i.e. with internal combustion engines) than hydrogen.

And it has nothing to do with solar PV or grid power, since few nations have enough land to make all of their transportation fuel from biomass, and biomass to electricity would put even more pressure on valuable land and ecosystems. 

Rick Engebretson's picture
Rick Engebretson on Apr 9, 2013

I like your fiber optic solar collector idea I K. Not sure about the steam engine part.

An optical fiber is also called an optical waveguide. And “fiber glass” is already used in roofing.

A lot can be done with photons captured into an optical fiber “glass wire.” The low efficiency of PVs is partly due to the fact sunlight has too many of the wrong colors and just over-heats the expensive semiconductor. A heat sink like you describe can be important.

My guess is you (or some kid in India) will be able to greatly improve your design long before the “nuclear experts” will figure out their many problems; including waste, proliferation, cooling water, grid infrastructure, etc. Perhaps that is why they prefer describing problems with solar to solving their own problems; they can’t.

It will be a remarkable day on TEC when nuclear advocates declare some progress with some of their own problems.

I K's picture
I K on Apr 9, 2013

You don’t necessarily have to transmit it across the sea although that is possible.

One option would be to go from west Europe all the way to east china which would get you a 10 hour time zone difference. Or you could go from west USA to East Europe via Canada- Greenland – Scotland which would get you a 12 hour time zone difference. Or go all the way around for a 24 hour time zone 

There are more benefits than just allowing a very high level of solar and wind. The immediate benefit would be to get rid of the need to ship fossil fuels around the world or even within your own country. Imagine 20 x 5GW lines across the globe. The USA could transmit 100GW of electricity to Europe rather than ship coal or gas to Europe.

Such a line could “virtually ship” the equivalent of 300 million tonnes of coal per year or 150BCM of natural gas. Each “node” can effectively import or export double this figure. So Europe could virtually import 150BCM from America and at the same time virtually import 150BCM from Qatar on the other side. No need for multiple massive very expensive and fairly inefficient LNG facilities and hundreds of vessels. No need to train millions of carts of coal across continents

It makes little sense to move billions of tonnes of fossil fuels around the globe when a relatively simple relatively cheap method of a global HVDC grid could do it very efficiently.

Before people say the electrical loss would be high, not necessarily it is fairly easy to reduce HVDC line losses just use a thicker conductor and aluminium is fairly cheap. The limit for the conductor thickness is that you can’t wind a wire above a certain thickness around a drum of a given size but there are easy ways around this. Eg vessels designed specifically for the task or segments of solid conductor fused together.

A world grid would have many benefits. Unfortunately to date because so few HVDC have been installed and so few companies offer the product the price for installing these cables is very high. Also in the past the political risk would have been seen as too high but considering we rely on other nations for food and energy already it shouldn’t been seen as a big risk anymore (especially since a global grid would connect all suppliers to all customers getting rid of single point risks like Russia cutting off gas to Europe (we would be able to instantly start importing from elsewhere if we had a global grid)

The actual aluminium content in the lines to wrap around the world 100GW of electrical lines would be in the region of $30-40B but you gain the ability to ‘transmit virtually’ billions of tonnes of coal and thousands of BCM of natural gas.

Stephen Nielsen's picture
Stephen Nielsen on Apr 9, 2013

You don’t see the breakthrough here, Nathan? The ubiquity of xylose doesn’t phase you at all? This will enable a phenomenal increase in the production of cheap hydrogen. 

 
The storage and easy utilization of hydrogen are different research areas, but research in controlled nanoarchitectures for the effective storage and catalisation of hydrogen is occurring at breakneck speeds.  The last decade alone has seen absolutely thrilling developments in materials science at the nano scale. Nano-materials with specifically tailored electrical, optical and mechanical properties have been produced and the rate of advancement and discovery in this area is increasing along an exponential curve.
 
Continuous pessimism about these rapidly advancing technologies is clearly unwarranted.
 
Schalk Cloete's picture
Schalk Cloete on Apr 9, 2013

Hi Willem,

Yes, it will be interesting to follow Germany’s progress over the coming years as it encounters more and more practical, economic and political challenges as solar and wind progress beyond 5% of total energy supply. However this great national experiment ends, the practical real-world experience will definitely be valuable. I just wish they chose a more efficient CO2 abatement path. The carbon intensity of the German energy system has hardly budged over the past decade.

 

Nathan Wilson's picture
Nathan Wilson on Apr 12, 2013

Sure, with solar power towers, adding storage makes the electricity cheaper (because the cost of the storage system is fully offset by savings from a smaller required turbine-generator).  With parabolic trough solar, storage costs more since the temperature swing is lower, but still is much cheaper than batteries.

I used to think that the storage issue meant that PV was a dead-end technology that would have to be displaced by solar-thermal in order for solar to fit in a zero-carbon portfolio.  But then I realized that most Gen IV nuclear technologies were also compatible with thermal energy storage. 

Nathan Wilson's picture
Nathan Wilson on Apr 12, 2013

“…when nuclear advocates declare some progress with some of their own problems.”

Rick, all of the “problems” you’ve listed boil down to the victory of propaganda over science (and that propaganda is largely promoted by fossil fuel interests).

So yes, every day there is progress with this problem.  The safety and environmental record of nuclear power continues to be enormously better than fossil fuel, in spite of the hysterical warnings of detractors.  The AP-1000 reactors under construction in China and Georgia as well as the SMR development programs move further along, thus proving that not everyone is fooled.

We environmentalists have for years unquestioningly accepted the claim that nuclear is bad.  It’s time to  ask the tough questions.  Here is a place to start reading:  The Nuclear Energy Option (Bernard Cohen’s free on-line book from 1990). For a more recent reference, I suggest Thorium – Energy Cheaper Than Coal.

Nathan Wilson's picture
Nathan Wilson on Apr 12, 2013

Concentration does not work without tracking.  Plastic does not last as long as steel and glass (though there have been attempts to use plastics to cost reduce CSP).

I K's picture
I K on Apr 13, 2013

The problem of nuclear is that of risk, not risk of radiation but the risk of arbitrarily being targeted for taxation and or closure and or market fixing to favour other types of generation.

Why spend $15B on a dual reactor when the state could tax you specifically, eg spent fuel tax in Germany. Or risk being forced to close your working plant decades early because a reactor the other side of the world built 40 years ago blew its top after a tsunami, even though there were no casualties from the nuclear part of the crisis.

Why risk building if the state is going to subsidise intermittent sources to the point that you need to pull back your reactor every day to make way for a couple of hours sunshine.

Simply put, the financial risks are artificially stacked against nuclear and even to a degree coal. So I don’t expect a notable increase in nuclear generation in the USA or Europe.  Elsewhere, where the state is in control directly or indirectly nuclear will grow because it wont face the same artificial risks. The state isn’t going to impose a spent fuel tax on state reactors nor close them 10 years after they start due to public misconceptions.

IMO the only chance of nuclear growing significantly is if china can build hundreds of reactors and get so good at doing it that a nuclear reactor can be built for not much more than a coal plant

I K's picture
I K on Apr 13, 2013

you don’t need to track the sun if the shape of the concentrating devise is symmetrical, ie imagine a sphere with the correct material and size so the focal point is in the centre. No matter where the sun is, the focal point will always be in the centre due to it being a sphere.

Put a fibre at that point to collect that focused light and use it to take that energy to somewhere useful, eg small PV cell or into a high pressure steam boiler to drive a turbine like coal plants do.  Glass would last centauries, plastic many decades and if built to last, centauries too.

I K's picture
I K on Apr 16, 2013

Land area is not really an issue, for instance if you covered 1 million KM2 of land in PV at 20% capacity factor locations you could produce a constant 20TW of electricity in a global grid, for comparision the world currently produces about 3.5TW of electricity. That would be considerably more than enough to meet all energy needs of a future of 10B people. With ‘just’ 1/500th of the earths land surface.

Alternatively imagine a world of 10 billion people, they will live in 5 billion homes. Say you install a 5KWp array onto each home that would give you 25TWp. At 12% capacity factor that is over 26,000 TWh of electricity without using any additional land. I know you could not install a 5KWp on each and every home but some can take more and a world of 10B will have plenty of commercial and industrial buildings too which can make up for the homes that cant install PV

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