Solar's hot, even when the sun is not
On the cloudiest day in the gloomiest weather, when I check my solar system I find it is still generating and exporting clean renewable energy into the grid. My solar system, like all rooftop solar systems, generates even when it's cloudy. That's because solar technology is able to produce electricity under diffuse light conditions.
Generally speaking, in the darkest, cloudiest hour on the gloomiest day, your solar system will be generating as much as 25 per cent of a normal clear day output. On a day with light cloud cover, your system could be achieving as much as 50 per cent of a normal clear-day's hour of production.
On the worst day in winter, the sky covered in thick clouds with only nine hours of daylight in Melbourne, my 100 square metre 15 kilowatt solar system still produces more electricity than my all-electric household's entire daily demand; and in summer on a cloudy day I'm still exporting significant excess electricity to the grid.
One of the reasons that cloudy day output is surprisingly good is that on cloudy days the surface of your solar panels are usually cooler, meaning that the solar cells themselves perform better. There is less light to cause the photovoltaic effect, which is how the photons of light get converted into electricity. But the superior operating temperature compensates considerably for the lower light conditions.
Today, solar panel efficiency is rising (in watts per square metre): the average panel would be 14 per cent efficient in optimal conditions, while SunPower, owned by French oil company Total (the market leader by efficiency), markets very efficient (albeit expensive) single layer monocrystalline panels at 18.5 per cent efficiency. Then comes Sanyo, who have a multi-layer panel which combines a conventional silicon wafer (what you see on most solar rooftops) with an amorphous layer. Today Sanyo are selling panels that have an 18 per cent efficiency, and are predicting they can rise to 30 per cent efficiency in the not too distant future, using this multi-layer technology.
Whether Sanyo or another technology wins out, within a decade we can expect solar panel efficiencies to double and costs to continue to decline significantly as a result of increasing efficiencies.
So in the future, when I swap my 15 per cent efficient solar panels for new 30 per cent efficient units, effectively I will be producing half the best output of today's panels even on a cloudy day. And in the future, anyone who wants the same performance on cloudy days as on clear days today will only need twice the roofspace, and in the worst clouds they'll be producing the same amount of electricity as in the best clear-sky conditions today.
Furthermore, my house and shed is 170 square metres – a fairly representative roofspace for the 6 million average Australian detached homes. And on top I have 5kW of rooftop solar panels facing north, 5kW of Solar facing east and 5kW facing west. My system can be producing significant electricity production in the early morning and well into the early evening.
The total annual production of my system in Melbourne is 18,000kWh for the year. For comparison, my all-electric house (heat pump hot water, induction cooktops, two LCD televisions, laptops, six heat pump heater/air conditioners and a water pump) consumes 4,000kWh in a year. Much of the 18,000kWh of production occurs on cloudy days as, according to the Bureau of Meteorology, Melbourne experiences 180 cloudy days per year. So the fact that rooftop solar produces when it is cloudy is an important one, that needs to be noted by anyone who is considering a solar system or planning solar for a 100 per cent renewable energy future.
Today, an average 170m2 house can produce more than 18,000kWh of annual electricity. There are over 6 million stand-alone houses and if all of those households had the same amount of rooftop solar as my house we'd (theoretically) be producing half of the nation's on-grid electricity demand. Of course, to achieve 25-50 per cent penetrations of PV we'd need to load shift much of what we and many of our businesses, such as water authorities, do at nighttime to daytime, pre-heat and cool our houses during daylight hours (sunny or cloudy) and we'd have to curtail some amount of production in summer. And of course in just 10 years time we'll be able to double our rooftop solar systems output, just by flipping the panels and inverters to new cheaper more efficient ones.
Oh and this is eminently doable – In Germany they installed 3,000MW of rooftop solar in December on their Christmas holidays when temperatures were sub-zero. That's equivalent to 200,000 Australian houses with the same size solar system as mine.
Rain hail or shine, solar will power on.
Comments on this article
RE: Would you install at real costs? REPLY Trevor Wood
Hi Trevor,
The answer is yes - in Germany the Feed-in-Tariff has dropped to 24 eurocents per kWh while the retail rate is 25 euro cents per kWh. Meaning that even if they removed the support mechanisms people would still install PV. But less capacity would go out as it would be net against your usage and not gross as is paid under the current EEG (Feed in Tariff) framework.
We would never buy 20% at 45cents a kilowatt hour. Feed-in-Tariff schemes have always been around to quickly drop the Feed-in-Tariff rate until it is no longer required.
So you might get 1% at 45cents and 2or 3 more percent with FiT support. Then you have people installing against their own usage (competitive with their meter)
and finally you have people installng and exporting down at 12 or 15cents a kilowatt hour
Re The use of the REC multiplier money was fine REPLY B Planet
Blue Planet,
Firstly I'm an advocate for all commercial renewable technologies. In days gone by I've been attacked by various quarters of the PV industry for being pro wind and Solar Thermal with Storage.
It's not about one viable renewable tech getting a leg up over another. There are basically four renewable technologies that are commercial and they all need support to ride the cost curve to parity with where fossil fuel sources are today.
The RECS are floored from day one, and should be replaced with a Feed-in-Tariff scheme. Most of the Solar and WInd in the world has been deployed on the back of Feed-in-Tariffs. The industry has FAILED to advocate for a much better policy framework and is paying the price.
Would you instal at real costs?
I can only speak for Queensland but if it was buying 20% solar at the current 45c/kwh, the cost of grid supplied power would double.( do the sums based on wholesale price of 7c/kwh, retail price 22c/kwh, and feed-in price 45c/kwh... maybe room for splitting decimals but close enough for discussion.) Now do your installation calculations based on unsubsidised equipment and feed-in at wholesale plus 10% for line loss savings and tell me it's economic... after all, who asked me to subsidise your savings via my bills?
RE: Daily usage REPLY Tony Smith
Edson Heat Pump boosted solar 707kWh per year.
Heating from heat pumps 1500kWh per year
more than 7500kWh heat delivered (22,000kWh for average Victorian home - though that includes serious losses through gases flue efficiency.
Fridge 328kWh a year
All house water pump (grid backup)
300kWh per year
5 laptops
2x 105 watt LCD Sony Bravias not used too much.
Miele Cooking - Induction cooktop and Oven
Renewable Hot water directly feeds MIele washing machine and Dish Washer.
Lights are compact flouros - can be halved again by moving to LEDs
A better Fridge on the market would save 20-30%
Re The use of the REC multiplier money was fine
Mathew - Quote from Giles P. "Since then, however, the RET scheme has continued in market failure. Despite warnings against it, the government allowed household systems such as solar hot water and rooftop PV to be included in the target, and in the case of PV, with a five-fold multiplier. The result has been a flooding of the market in such proportions that enough renewable energy certificates (RECs) will be deemed in 2011 to satisfy a 20 per cent target." http://www.climatespectator.com.au/commentary/ret-hail-fellow-not-well-met
No other renewable technologies have been given a leg up in the manner the solar pv has. Indeed GP noted that these RECs were snapped up by both Origin and AGL and have satisfied their requirements for some time to come until the scheme was spit into SREC and LREC. It's meant other technologies have been discounted by up to 80%. You can't be in business if a policy discounts what you do by 80%. And these RECs were treated as if the power was continuous which it isn't.
RE : My peak winter usage is 14kWh in a day.
There will be a day this winter that your 15kW of solar generates < 14kWh of electricity. pvOutput has some of the best systems, yours isn't any better. And they have plenty of 0.5kWh/kW days, ie only covering half of your highest consumption day which will coincide with worst production. Thats the fact with rooftop solar, not enough output when you need it most.
Daily usage
For comparison, my all-electric house (heat pump hot water, induction cooktops, two LCD televisions, laptops, six heat pump heater/air conditioners and a water pump) consumes 4,000kWh in a year.
Mate - I work in solar and see about 1200 power bills per year. There is no way all that stuff above is only going to consume 10.9kwh per day (unless you don't switch any of it on).
Rough guess, you'd be looking at more than 40kwh per day.
Re David Osmond 19%
Matthew said "On the cloudiest winter's day in Melbourne, a 15kW rooftop PV system can still produce more power than a household's daily demand"
David, you have used an average of 19% when you have stated that the "cloudiest day" it only did 8%? By Matthew's statement above, you have to choose "the cloudiest winters day", not an average of bad days.
Without knowing your postcode
Of course I'm only guessing at the worst day as I don't know your postcode. Here's another 0.313kWh/kW from postcode 3107, a system that does 7.6kWh/kW on a good day. Please note that rainy day performance is 4% of a good day.
http://pvoutput.org/list.jsp?o=gss&d=asc&id=958&sid=753&sg=1&se=1&gs=0&t=0
That would make <5kWh from a 15kW system. In the middle of winter. These are the facts. Your system isn't magical, you can't produce any more electrons than others when the sun isn't shining.
RE: So no data REPLY S Cooper
I have 7.42kWh of production recorded for 03 July 2011
That's much higher than the 0 you were claiming that I would have had and proves that with an additional 10kW that I will have in the 2012 winter I will more than ride out each day of winter with a surplus.
My peak winter usage (from heat pump heating and heat pump hot water predominately) is 14kWh in a day.
My usage drops down signifcantly in Summer.
My gloomiest days generate ~19% what they do on the best days
Hi Jeremy, I live in Canberra and also have my system providing data on pvOutput. You can see my data at:
http://www.pvoutput.org/aggregate.jsp?id=4250&sid=3340&v=0&t=m
I’ve only got about 9 months of data so far, but for those months, the worst day of the month has generated between 8% and 36% of the electricity of the best day of the month, with an average value of 19%. So Matthew’s claim that the gloomiest day generates as much as 25% as what it does on a clear day is a touch on the high side for my system. However it is not far off, and with his mixture of orientations it certainly wouldn't surprise me if the figures for his system were indeed about 25%.
regards,
Dave
Who pays the transmission losses? REPLY John S
We pay for distribution losses on our bills as consumers. There is a factor applied to electricity that is sent to a reference node on the network. Thomastown in Victoria.
You can be negative losses (like a PV system would be on the grid).
Average losses for Victoria are 7% however they are average and do not take into account that they are much higher during peak power events. Are probably as high as 20% during these peaks but it is difficult to get this information.
The Think-Tank is wrong about the level of compensation for a PV owner for each unit sent to the grid. PV owners contribute an energy service that no other generator offers. That is they bid in at $0 - and they always bid in daily reliabily. This causes wholesale price (Spot price) suppression. At a per capita penetration level the same as Germany's the spot market would have 2 billion routed out of it. This saves all consumers. If utilities are already contracted when these contracts come up for renegotiation this effect will wash out in the market.
And PV owners bid in no matter what, no gaming.
IT is called "Merit Order Effect" and the University of Melbourne Energy Research Institute has written a detailed paper on it for the Australia eastern seaboard energy market. -- applying MOE benefit means that a Feed-in-Tariff of 35cents per kilowatt hour pays a dividend to all consumers and adequetly pays prospective solar system owners to go ahead and invest in our future.
French Nuclear Power
Srephen Gloor
I guess we need both :)
Germany
Retired - no affiliations - and I only reveal my name on blogs which I am faliliar with.
French Nuclear Power
John S - "It would have been a very uncomfortable 2 weeks in Germany without those nuclear power stations."
As would it be uncomfortable in France in hot dry weather:
http://nuclear-news.net/2011/11/30/france-stops-nuclear-plant-due-to-hot-dry-weather/
"Dry weather conditions are starting to hit output at France’s nuclear reactors with EDF forced to stop one reactor in northern France to protect river flows,"
This is not the first time this has happened BTW.
The energy supplies in Europe are all interconnected and German solar/wind often supplies load following for French nuclear that would prefer their reactors to stay in baseload mode.
So no data.
Ok, so you don't have data from last winter. What point is it saying "On the cloudiest winter's day in Melbourne, a 15kW rooftop PV system can still produce more power than a household's daily demand"
When your system has not even been operating in winter?
or in your words if you are stupid enough to install
The use of the term stupid was yours.
You putting panels on your roof was a great effort and must be applauded even if you have some ideological bent against improving health of the world's people and decarbonising the economy.
The great effort you put in by taking advantage of the scheme, putting your own private money up (or leveraging to pay for it) means that future panel installs for providing the 5 billion people in the world who don't have elecricity will be much cheaper and affordable.
When the world is on 20% solar and they are recieving that electricity at much cheaper than today's grid electricity you'll realise that what you did was right.
Who pays for transmission losses?
There was a paper recently from one of the Economic think tanks that FIT should be the wholesale price of electricity. ( Similar I guess to WA).
The argument went along the lines that the electricity distributers still needed the infrastructure to provide for peak demands.
This does not take into account spot pricing that can be many multiples of the average.
Also, does anybody know what the distributers pay for - is it ex generating facility or is it the usage at the end point or some place in the middle. The reason for the question is “Who pays for distribution loss? The generator or the distributer”
If it is the generator, then FIT should be more than wholesale price because there is generally no transmission losses with locally generated electricity.
RE: Germany REPLY John S
Another one that doesn't disclose his full name or affiliations/ Business interests.
Baseload power stations in NSW use much less than 70% of the coal at night.
The average capacity factor of NSW baseload coal plants is 63% annually. Night time average would be below 50%.
They are incredibly inefficent.
Germany has been going fine and has had lower wholesale spot electtricity prices than France even after they removed half their nuclear fleet.
or in your words if you are stupid enough to install
Can you please re-read my posts befor you use statements like "in your words"? You will find I said the NSW gFIT was stupid. People that took advantage of it got a great ROI of about 20%, why exactly do you think I did something stupid?
The NSW system treats your shaded system fairly
I never advocated RECS, have always advocated Feed-in-Tariff over RECS. We have to use what is available while its available and then transition to a better production based system. No problem there.
PV is not subsidised when an appropriate Feed-in-Tariff level is set (say 35cents per kWh) due to the Merit Order Effect. Look it up.
60cents kWh was too high, but a small mistake on ~350MW of installations. We have Germany installing 3 times this amount in just one month.
As for that production you were looking for.
Production figure for July 03 2011 was 7.42kWh on my PSA5kW grid Tie with Baterry backup inverter.
I did not have logging for my other inverters as they were not yet installed. But it is fair to assume that it would be 23kWh total if it was all north facing but because it isn't and its winter then 18kWh total would be safe to assume.
I do not have my specific usage logged for the date you are requesting. However 18kWh would mean an extraordinarily high use of my zoned heaters (they produce over 5kWh of heat for every 1kWh of electricity to drive the refrigeration pump)
The day before and the day after were twice as much production as this day.
The NSW system treats your shaded system fairly.
No, because its not the only subsidy. There is also RECs as you well know. The NSW gFIT was the sole reason for installing solar for many of the 100,000 households that signed up. Sure we don't get as many $ in the shade, but the RECs don't change. So its the opposite of what you say, the NSW gFIT made it cost effective to press ahead with shaded systems. I was one of them and I know of plenty of others. The only fair system is one that is not subsidised. And yes I know coal is subsidised too.
Germany
Germany
One of the nice things about Base Load output from coal fired power stations – late at night – is that they still use 70% of the coal that they do during peak load.
That means that all those yet to come electric cars can be charged without any increase in the use of non-renewables.
It would have been a very uncomfortable 2 weeks in Germany without those nuclear power stations.
You can not have 100% renewables without efficient storage.
Why are you now comparing to my system?
I have provided data for other systems in Melbourne, yet you have now changed the topic. I was only disclosing my system as you wanted to know "my agenda". I know my system doesn't perform as well as yours so never used it to discuss your unsubstantiated claims. Instead I used one of the better performing systems in Victoria. Lets stick to the facts rather than mudslinging which is getting us nowhere.
My agenda is simple, to gets some facts so people can make an informed decision. Saying that 15kW will produce more on the worst day than your house consumed is simply wrong. Otherwise you wouldn't need batteries at all. Don't you see that your article is not factual?
RE: Cloudy day monitoring
Unlike your system, my system has no shading, and it produces significant energy on the worst cloudy winter days. I have told you that already.
The NSW system treats your shaded system fairly. If you choose (or in your words if you are stupid enough to install) a system that is shaded. Then the Feed-in-Tariff will only pay you for the reduced amount of production that you make.
It is a production based incentive. Not an upfront incentive. It is one reason why Feed-in-Tariffs are so successful. Is that they make people think twice about installing solar panels where there is shade.
RE: Germany REPLY John S
France is propped up by its interconnections to Italy and Germany.
It's nuclear sector is so inefficient that it has to dump night time power (when no one wants it) on neighbouring grids predominately Italy.
In fact out of 74% of generation attributed to Nuclear in France. 35% of that is dumped on neighbouring grids at night.
Renewable countries like Germany, Austria, Spain and Switzerland are propping up the Nuclear dependent French by taking all their surplus electricity.
The French have realised this Foley and the soon to be incoming socialists will order a phase out of 50% of Frances nuclear capacity. That's their policy.
RE: Cloudy day monitoring
Ok, so we have the facts from 100's of rooftop PV systems on pvOutput.org vs your hype, which you refuse to backup with actual data. Which should the average reader believe?
So now you say 3 out of your 4 inverters switch off during the darkest days (and the 4th is only on because its battery powered, otherwise it wouldn't be on at night either!). Thats different to what you said in the article.
re "You aren't even willing to disclose your first name or business interests."
No-one ever asked until now. My first name is Jeremy, I was, am and probably always will be working in an industry TOTALLY unrelated to solar, energy or anything of that sort. I have 10kW of panels spread over the roof and ground. Some is shaded, but due to the stupid NSW GFit it was still worthwhile.
I am happy to provide actual solar production from my system for all to see, unlike you.
http://www.pvoutput.org/aggregate.jsp?id=224&sid=1381&t=m
With 10kW I am producing more than I consume, but it doesn't correlate at all with my consumption. You can only cover your consumption by using storage, and as you say you don't because its not cost effective to destroy your batteries.
Please stick to facts. So what was your production & consumption on July 3 2011? 2 numbers, thats all. A couple of facts.
Roof top solar and other rene-ables
Firstly lets get this straight; PV wind thermal solar etc only produce electricity, while electricity is a form of energy all our energy usage cannot be supplied by electricity. In fact electricity only accounts for about one third of our primary energy usage. While we may be able to source 100% of our electricity from renew-able production our modern economy/society would not function without fossil fuels. The reason we need to conserve those fossil fuels for the future by installing as much alternative infrastructure and renew-able power as quickly as possible.
Dan
RE: Rubbish
On your numbers
2kWh minimum in a day on a 3kW (Not 3KV) system would mean that a 15kW system would produce ~10kW in a day.
Depends on orientation - the day in question and
The output you quote would meet my winter demand.
Germany
There was a 2 week period just recently when Germany had to import power from France.
The wind had stopped and the sun ceased to shine.
You guessed it, it was France's nuclear power stations that provided the power - just as they did last winter for the UK when there was a particularly cold snap.