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Electric power substations like this on in Japan will become increasingly important in micro-managing local power grids.
Electric power substations like this on in Japan will become increasingly important in micro-managing local power grids.


Electric Cars: Will the Cure Be Worse Than the Disease?

By Bill Moore

Imagine you built a car plant that could produce 100,000 vehicles annually. Despite a huge capital investment, you only really intend to build between 20,000 to 30,000 annually. You're either expecting sudden, unanticipated demand at some unforeseeable moment in the future... or you're an electric utility.

That's the point Bill Shanner wanted to get across to me this week as we talked for nearly an hour about the realities of the electric power industry; why some types of utilities like the idea of electric cars and others very much don't.

All of us in the developed world expect that each and every time, regardless of the time of day, we throw a power switch, the electricity will flow: lights will glow, microwaves will run, air conditioners will cool and computers will go 'ping" as they boot up. Live in other parts of the world where the grid is wobbly at best or just doesn't exist and it's a different story.

The problem and the opportunity -- depending on your perspective -- with adding millions of grid-charged vehicles, be they plug-in hybrids, extended range EVs, or pure battery EVs, is that they do add load. Yes, there is currently sufficient overnight generation capacity, but from the utilities' perspective, in order to keep a comfortable reserve they have one of two options: build more capacity -- especially on the transmission and distribution side -- or buy power from someone else, typically at rates, Shanner explained, 10 to 100 times what it costs the utility to generate its own, which is, on the global average, about 2¢ a kilowatt hour. But buying power from someone else doesn't solve the problem of distribution.

There is, however, a third option emerging: the smart grid, but Shanner's view is a bit different than what you're used to hearing. The reason utilities are interested in the smart grid is so they can shift the risk of electric power availability to the consumer. There are very pragmatic reasons for this having to do with how the utility industry has evolved.

The industry is divided into essentially three types of power producers: investor owned utilities or IOUs, electric power cooperatives and municipal power companies; and depending on which you are colors your view of electric cars.

As Shanner explains it, grid-connected electric cars are a lot like air conditioners in that their load is fairly unpredictable, largely because despite incentives to shift charge times to off-peak hours, EV owners are going to charge when and where they feel they need to. I can appreciate that because even though most of the time I usually plug in our converted Prius after 10 pm in the evening and unplug it before 8 am in the morning, there have been several times when I've wanted to charge it during peak hours. Now, with one such car in the entire state, and region for that matter, this isn't a problem. Even a few thousand grid-charged cars wouldn't be that big an issue for the grid. Millions of such cars, however, will be.

It is the unpredictability of this load that is worrisome to electric power planners. Enter the 'smart grid,' which from my confidant's perspective is the electric power industry's way to get the consumer to accept more of the capital investment risks that heretofore in a more monopolistic, vertically integrated power industry, the utility would have to bear.

Case in point: Vehicle-to-Grid (V2G) electric vehicles. It isn't the utility that is buying all that energy storage capacity, it's the car owner who is assuming the capital costs. Solar PV on your house? Same story. You're assuming the investment risk, though even here, you're counting on the grid to swap power with you: expensive solar during the day for cheap coal, natural gas and nuclear generated power at night. You're still bearing the lion's share of the cost. In fact, renewables like wind and solar don't reduce the need for grid capacity, they increase it because of their intermittency. A million solar roofs may work fine to help ameliorate some mid-afternoon air conditioning load, which is really what all the excess capacity was built for. It's like that 100,000 car per year plant that most of the time only turns out a few tens of thousands of cars annually. And since most of those solar PV installations haven't invested in banks for back-up batteries to handle night-time loads, the grid still has to provide all those homes with power after the sun goes down or when its not shining, like it's been here in eastern Nebraska for what seems like weeks now.

According to Shanner, two-thirds of the capital costs of the grid are T&D, transmission and distribution. It's all those wires, towers, poles and substations needed to get the 'juice' from the generator to our wall outlets. It's all those millions of neighborhood transformers that once two or three Volts and Leafs start to appear in a neighborhood will need to be replaced every 12 years instead of every 17 on average according to Arizona State's Power Systems Engineering Center.

Two nations, Korea and Denmark, have begun developing strategies to deal with the problem. They realize that the grid needs to be managed much closer to the load than it presently is. Under our current regime, utilities manage in 100MW blocks of energy, either in terms of production or buying and selling on the spot power market. In Denmark's case, Dong's wind power is sold to a central power pool and then resold to individual substations. What's happening is that the power company is starting to practice the same production strategies car makers adopted decades ago: lean [power] production, just in time [power] delivery and activity based accounting.

In effect, what Korea and Denmark are doing is moving energy management down to the substation level, making each a separate profit and loss center in their business model. But ultimately, that means increased electric power costs, not less; costs being borne more and more by the power consumer.

In fact, for any of this to work, it is Shanner's contention that there needs to be a complete transformation of the electric power industry business model; and the price tag to do it will run into the trillions of dollars; a lot of it being spent to buy up stranded utility assets, as well as expand and upgrade the T&D system. What's needed is both improved macro and micro management, plus a far more heterogeneous power grid instead of the hodgepodge we now have to live with.

To illustrate his point, he said that Intel has three production facilities in Silicon Valley, one in San Jose (PG&E), one in Santa Clara (a well run muni) and one in Sunnyale (a cooperative). All three charge Intel different power rates. You can probably figure out which charges the highest rate. There are 2000 distinct electric power monopolies across America, and each has a different business model and consequently a different view of the coming of electric cars. The IOU's (and their investors), as well as coops, generally speaking, see EVs as another profit stream because they make their money on the margins, around 12% Shanner estimates. If their net revenues go from $1.5 billion to $1.515, so much the better. The more power they sell, the more profit they can make. For the municipal-run utilities like Omaha Public Power District that produces the power to keep my lights on, iMac running, and Prius recharged, electric cars are a liability requiring more capacity that has to be built at the expense of the rate payers for whom they work.

I won't pretend that I understand all the delicate nuances of a very complicated industry, but Bill Shanner certainly seems to have a good grasp of it and if he's right and we don't do this carefully, in his words, "the cure could be worse than the disease."

Published: 21-Jan-2010 | Page Views: 3995
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26 comments so far...

1.
22-Jan-2010
80437 		   Omaha does have plenty of wind generation potential!
Posted by: john hurt
2.
22-Jan-2010
80445 		   The real answer to this problem is "hybrid houses". Just like a hybrid car uses it's battery to help power itself during acceleration if each home had a power cell that was capable of sustaining the house for several days most the grid fluctuations would go away. For lack of a better description a battery of some sort could be used, it doesn't have to be light or small, a 3 foot cube would probably work. These batteries would get recharged from the power company during off peak hours. Houses would never know if the power was out, heating systems wouldn't go down in storms, and we would already have all the power plants that we need. Electric cars could be recharged from this "battery" and avoid the problems of charging only during off peak hours. Don Zacher
Posted by: Don Zacher
3.
22-Jan-2010
80447 		   Distributed renewable generation and some short term energy storage(pumped hydro or compressed air storage)can overcome most of what he is talking about. Look at the Kasel Germany Combined power plant study that shows that renewables can provide 100% of electrical needs. In Michigan 10% of Consumers Energy and DTE Energies electrical sales are "stored" in the State's one pumped hydro facility. It is important to decouple the utilities' profits from the sale of electricity so that energy conservation can be maximized.
Posted by: Wayne Appleyard
4.
22-Jan-2010
80448 		   Most people tend to buy the same product at a cheaper price. I. e. make the price for power at a charging station during daytime (scarce provision)3 to five times as expensive as during the time period between 20:00 PM and 5:00 or 6:00 AM. I'll bet my bottom dollar that 99 % of the problem will be eliminated.
Posted by: yoat mon
5.
22-Jan-2010
80455 		   Excellent article, Bill.
Posted by: Carlos Ruiz
6.
22-Jan-2010
80461 		   Hello Bill, Yes we need to be mindful of the medium and long term impact of developing and adopting EV's. However, in the past 20 years we have seen something like a 50 fold increase in the electric power demands for PC's, Cell Phones, and WideSceen/DVD's, battery power tools.....They individually draw much less power than a EV but there are mulitudes of them in almost every household and business. It will take decades for EV's( I hope, finally) to manage even a tenth of the market penetration. If the cost of electricity goes up much, small site wind generators and solar panels will become more and more cost effective. AND the individual homeowner will have some real control. Buy a site renewable system and pay for it with the money you don't send to the mega Corp. That is what really worries the Utilities and Corp. America. Marion Zaugg
Posted by: Marion Zaugg
7.
22-Jan-2010
80464 		   As someone who lived for over 18 years 'off the grid' I found the comment on hybrid homes somewhat amusing. Although I had a home and shop that were light years ahead in terms of efficiency as compared to the vast majority of existing power users power storage was always a problem,. I had both a large wind turbine of 2k as well as 1kw of PV and lived in a fairly windy and sunny place. The biggest headache I had was ensuring enough energy storage and I had a bank of batteries at least 5 times larger than the suggested 3 cubic feet. Batteries are now no better than they were then,and don't appear to be getting multiples better and cheaper in the near future so let us just see this hybrid option as a nice dream but not reality.

Bill's article just serves to illustrate the monumentally complex issues we will be addressing as we transition from a fairy tale world built on oil and coal that were as cheap and abundant as dirt, to a future were we have to deal with an overpopulated world starving for scarce resources with clean water and air being of primary importance. A future choice of electric power may be the least of our worries.
Posted by: lawrence Elliott

8.
22-Jan-2010
80471 		   My brother J lives in India where the power company is especially unfriendly to the (mostly) farmers that live on his segment of their grid, because the farmers mostly steal power. So, the utility provides power for only 12 hours per day. J has been forced to buy batteries and an inverter to keep his fridge cold, his lights on and his computer up. Though his power needs are less than those of an American house, the cost of batteries (lead-acid, roughly US$ 1500 every 2.5 years) is pretty high even for a two person house without many US-style amenities. As is so much the case with evworld, batteries are the critical element. So much research, so little development. And such a game-changing component if only it had higher performance and lower cost. We have 3 KW of solar, and I would go off the grid in a minute if adequate batteries were available.
Posted by: keith gunn
9.
23-Jan-2010
80526 		   All of those battery disbelievers can log-on to MIT and Stanford's websites to read about all of the breakthrough battery technologies that are comming to your battery retailer very soon.Disbelief of battery technology advancements is like disbelief of electronics technology advancements.Sorry all disbelievers but the battery Genie is out of the lamp and will not go back in.
Posted by: john hurt
10.
23-Jan-2010
80529 		   About the T&D problem: it's like a breadfactory that complains it just can't sell the people more bread if demand increases because it would involve buying more trucks to get it to the supermarkets. If people like Bill Shanner (Scammer really...) were in the food industry we would all starve to death. About increase of power production: has there ever been a utilities campaign against airconditioners like there is now against EV's? Seems these appliances generate a lot more disruptive demand pattern on the powergrid than EV's would. Yet everybody has them and the grid has adapted. That's how markets work: suppliers adapt to increases in demand. Beware there is a well organised FUD campaign against plug-in technology going on and FUD pretty much seems the name of Mr. Scammer's game. Well that or an excuse to charge people more for their power.
Posted by: Chris O
11.
24-Jan-2010
80634 		   With the advent of smart grids I feel this will handle itself over time. In the beginning I see the EV being a potential drain of the grid. But I see more than one thing going on at the same time. While we are switching to EV's, more and more homeowners, etc will be installing PV's. (I'm trying for a ten KW for my home this year). In the beginning these PV's and more conventional power will be used to recharge the EV's. But in time this will reverse itself. The batteries in our EV's will become the storage cell for our homes. During the day the sun from our PV's will charge our vehicles. In the evening, and during high peak usage, the grid will use our EV batteries to smooth out the peak loads. Then after the peak, the conventional power will recharge our EV's. If there were 10 million EV's each with a 100KW battery that's a 100mw of power that can be used to smooth the curve. That's a lot of power.
Posted by: Joseph Like
12.
24-Jan-2010
80649 		   One simple-seems to me- is the use of automatic cut-offs. Here in Ontario, I and many others receive a $25 inducement to sign up to have my air conditioner shut off when there is danger to the grid. The electronics to control shut-off at times when power costs are high would seem to be within the let's do it window. I plug in my electric trike when I return home, often during the day. It would be nice to be able to buy a devise for my outlet which would only feed in cheap power. Electric cars..same deal- good for the consumer- good for the gridd???
Posted by: ron mccurdy
13.
24-Jan-2010
80661 		   SMRT GRID, Time Of Day pricing, these are basic items to make smarter customers and loads. Let's use them. Anyone with a plugin hybrid should never plugin during peak times. They can always get home and charge off peak. Each and every person and load counts !
Posted by: Jim Stack
14.
26-Jan-2010
80819 		   There are emerging technologies that will completely change the picture. First, fractional Hydrogen. BlackLight Power has been developing this new source of energy for almost two decades. Rowan University and GEN3 Partners, who advise Fortune 100 firms, have done experiments which support their claims. However, even though 6 utilities, including PacifCorp and Conectiv, have agreed to purchase more than 8,000 megawatts once electricity becomes available, very few with scientific background are ready to accept this new source of energy as real. BlackLight claims they will demonstrate 50-75 kW prototypes this year and megawatt plants within two years. Engineers and scientists at our own firm disagree with the theory developed by Randell Mills at BlackLight, but not with the reality of fractional Hydrogen. We agree that this new energy source allows a barrel of ordinary water to become the equivalent of 200 barrels of oil. We call fractional Hydrogen ECHO(tm) - Energy from Collapsing Hydrogen Orbits. It will make possible a SPICE(tm) - Self Powered Internal Combustion Engine. Such engines show promise for powering hybrid cars and trucks. As hard as it may be to believe, a gallon of water might power a hybrid for 1,000 miles. Time will tell if this is an accurate possibility. Magnetic generators, MagGen(tm) are even more difficult to believe. However, both solid-state and rotary variations look increasingly practical to our scientists and engineers. Until confirmed at independent laboratories such as EarthTech International and Lawrence Berkeley, we believe skepticism is fully justified. Their have been many claims and outside of our own experiments they, so far, do not appear valid. However, a solid-state 1 kW generator seems likely to be on the horizon. Since I have been overly optimistic in the past, I won't hazard a guess as to just when it might appear. When it does, a pair of these should prove capable of replacing the plug on a plug-in hybrid. Once in mass production, both of these revolutionary systems will make possible suitably equipped and parked cars as power plants. Where a plug-in hybrid equipped with a 2 way V2G plug can sell up to 25 kW to the grid and earn, according to the Delaware studies, up to $4,000 each year for the car owner - these vehicles, which have been called Super V2G will be able to provide up to 150 kW to the grid. No wires required. The car or truck should also be able to power a home or business. These developments are on their way. Now the task is to accelerate development. Imagine the implications!
Posted by: Mark Goldes
15.
28-Jan-2010
81024 		   Some thoughts. (1)Utilities do not have profit margins. They are regulated monopolies and earn a return on their capital investment. (2) Electric vehicles may cause problems,but they will penetrate the market slowly and as we build a smarter grid we will have more options to control charging with price signals and active control. (3) Some problems can be mitigated if we stick to PHEV with on board charging or motive backup with fossil fuel.
Posted by: Bruce Bentley
16.
28-Jan-2010
81040 		   The thotful responses to this subject show a good awareness of smartgrid technique, load-management, and power-conservation. I believe that EV drivers can help utilities/cooperatives plan their grid op erations to provide charging energy at reasonable cost without having to overbuild or oversize their generation and distributing facilities. All wastef ul energy-consumers [24/7 lights under gas station canopies, 'driving range' car dealership lot-light ing after closing time, bright-white mall/shopping center parkinglots, advertising billboards when no traffic is passing by, all upward-lighting except weather-observation and 24/7-flown US Flags, etc.] shud be extinguished when not needed. Distribution voltage shud be raised enuf to better-utilize wire gauge of extant plant. Capacitor banks which cance l out wasteful 'reactive load', 3-phase 240-480VAC service to small businesses and large residences to improve efficiency shud be designed and made co de--just as the change from 120V/2-wire to 240V/3- wire did. Wiring small biz/residential energy-cent ers [breaker boxes] with un-interrupted service to most lighting and important 120V appliances [alarm systems, ceiling fans, garage door openers, etc.] and 'interruptable' loads like residentaial batter y banks, air conditioners, electric clothes dryers , water heaters, and BEV chargers[!] thru utility/ coop 'interrupter' relays controlled by 'ripple-co ntrol' or digital command from the grid...Another neat trick is to wire large-motor starting contact or relays so that every time large motors [air com pressors, heavy water heating elements, etc.] are energized, the three 'legs' are 'lifted' from less er loads [small water heaters, the cooling parts of soft drink vending machines, small air conditio ners, window fans, etc.] for the time the large el ectric-consumer device operates: When the relay drops, the minor loads are restored--they do not function when the 'heavies' run! Finally, the next time YOU drive by or thru a fastfood store note if the big signs and lot/soffit lights are on--during the daytime when the sun is shining...There are ve ry many unnecessary loads left on due to negligenc e: If they were removed, we cud gain the energy to recharge BEVs...Aaron Allen...
Posted by: Aaron Allen
17.
28-Jan-2010
81059 		   Two points:

1. What has "helped" in other industries? COMPETITION! Let the best "power producer" win, according to market share. Force the monopolistic power companies to share their facilities, and give the consumer a choice whom to buy power from. The one that has the fewest brown/blackouts will win, and it will force all of the power companies to become more efficient and less costly. Don't allow half measures; you'll end up with California!

2. Beware the "smart grid" technology that is based on Zigbee technology!!! It is an extremely insecure wireless technology used in all kinds of devices, including power plants, electric meters, thermostats, and soon to be in dryers, furnaces, electric ranges and ovens, A/C units, etc. A great idea, however, an infant in the security world and already fully hacked.
Posted by: Alex Moen

18.
28-Jan-2010
81065 		   But it is NOT unpredictable with millions of cars. It is very predictable. At no point will all million cars plug in at exactly the same time. People will be plugging in and unplugging whenever the feel like but when you have a lot of people, it all averages out to be withing a very predictable range. It is known as statistical multiplexing.

It is just like political polls . . . once you poll a certain number of random people, you can be certain that the result is within 3% of the correct value.

And before you hit that large number of cars, the small number will be so insignificant that it won't even register. Adding a Chevy Volt is not that much different that adding a new refrigerator.
Posted by: Don Jackson

19.
28-Jan-2010
81071 		   As crazy as it might sound, I believe our country should seriously re-visit the feasibility (as I understand it, a study has successfully been done) of an orbiting solar collector. To make it an international effort would serve to mitigate the overall expense. Individual countries would likely have their own microwave-receiving stations. I'm led to believe that its cost would be little more than the trillions you are already mentioning.
Posted by: Tom Connelly
20.
28-Jan-2010
81078 		   Smart Grid? Well, last month, I attended a lecture on the Smart Grid by Southern California Edidson. I was blown away by the cost of Smart Grid system, $110 billion. According to Edison, that's more than last 10 years of their investment. I don't know who's going to pay for it, I know it's not going to be Edison, if they do, how much are we going to pay for future electricity? Right now, we(tax payers) are paying for most of their R&D through DOE grants.
Posted by: Keith N
21.
28-Jan-2010
81079 		   I have studied the problems of managing the grid and have books on the subject. However, I question statements that electric cars would result in unduly unpredictable loads on the grid.

Power companies have the technology to shut off appliances that use large amounts of power. For example, the local power company has paid me for the ability to power down my central air conditioners.

Studies have shown that shutting down air conditions at hotels and other large buildings can reduce the load considerably. That means that if there is a sudden increase in load that the utility cannot immediately meet, it can shut off air conditioners for a few minutes to give it time to start the peaking plants. They do not want to run the peaking plants more then necessary since they are inefficient and use expensive natural gas. So, being able to shed part of the load for a few minutes is good for all of us; it increases efficiency by reducing the need for spinning reserve and reduces green house gasses.

Most of the power is generated by base load plants which, to maximize efficiency, are designed to run continuously at 100%; they cannot easily be throttled down. There are also load following plants which can be throttled down, but not without losing efficiency and not quickly. Peaking plants can be started fairly quickly and can load follow well, but are inefficient. A certain amount of spinning reserve has to be maintained to be able to adjust for sudden increases or decreases in demand.

Managing the grid is not an easy thing to do. Doing so efficiently to use as little fuel as possible requires being able to predict power demand accurately.

Regarding battery electric cars, utilities could be provided with the ability to adjust the cost of power according to the time of day and load on the system. That way, BEV owners who charged at off-peak times would pay less for the power. Utilities could also be provided with the ability to suspend charging briefly until they could activate more generating capacity. That should eliminate any problems that utilities have with BEVs, even if BEV owners conspired to plug in or unplug all of their cars at the same instant.

Wind turbines can create serious problems for utilities. Experience in Europe indicates that utilities cannot efficiently accommodate wind turbines that can generate more than 20% or 25% of the power generating capacity. That's because the wind is unpredictable and always changing; utilities cannot accommodate the sudden changes without losing efficiency. With wind turbines on the grid, utilities have to maintain enough spinning reserve to accommodate the sudden changes, and that requires burning more fuel. Although it helps to have the wind turbines spread out over a large area so that they are not all affected by wind speed changes at the same instant, it still creates problems. So, with currently available technology, it is not clear that wind turbines actually reduce our use of fossil fuels.
Posted by: Frank Eggers

22.
28-Jan-2010
81109 		   Responsibility needs to start at home, literally and figuratively.

Batteries are undergoing the kind of maturation we saw for so long with computers, but not at quite the same rate: batteries have increased in capacity significantly since the advent of the EV-1, and with the help of nanotechnology, may undergo much steeper increases in energy density and reduction in cost very soon.

Should that happen-- and I'm sure it will-- homeowners can take responsibility for their own energy needs, and the dour scenarios Mr. Shanner envisions will never occur.

Air batteries being developed at IBM, University of Arizona and elsewhere eliminate the weight and expense of the cathode of the battery and replace it with a simple membrane that allows the anode to swap electrons with our atmosphere, which, if it works as hoped, can mean a tenfold increase in capacity.

A Tesla that gets, say, 240 miles per charge could, with air batteries, drive 2,400 miles per charge-- with such a massive increase in charge density, there would be far less fluctuation in demand for plug-in charge capacity. EVs would not need to be charged every night; smart charging would make it much less an issue.

The same battery, cheaper by far than the batteries we have today, would make home storage batteries much more practical. With enough battery and PV capacity, homeowners can opt to go totally off the grid, staying connected only to provide energy should it be needed (in emergencies, that same bucket of electrons that costs the utility companies 10 to 100 times as much from neighboring utilities can be bought cheaper from homeowners, and both the homeowner and utility company can benefit financially from the arrangement).

Another battery advance will require cheap carbon nanotubes(CNTs), which until now have been rather expensive, but Micro Bubble Technologies, among others, claims to have techniques for making them much cheaper. With cheap, plentiful CNTs (and there are dozens of variations) of the right type (some are highly conductive, others are semiconductors), internal parts of the battery can be coated with CNTs that dramatically reduce internal electrical resistance. That makes the batteries last much longer, gives them greater charge density, makes them run cooler, and increases their C rating (a measure of how fast the batteries can be charged and discharged without damage}.

With the lower internal resistance of these batteries, it costs less to charge the batteries; this is good for the utility companies whether they store the energy themselves, or homeowners do.

Most motors today, including those used in EVs, are remarkably efficient. But power generators are not, with efficiencies more in the range of 70 per cent or so. One California R&D (that will remain anonymous for now) appears to have found a way to increase generator efficiency dramatically; if that is the case, even a few per cent can mean huge differences in just how much fuel will be needed to power our society, and how much it will cost to provide that energy. EVs use regenerative braking to increase their efficiency and extend their range between charges; an explanation of the dynamics are complex, but because the motors are serving as both motors and generators (for braking), a motor efficiency increase of, say, 5 per cent can mean an increase in overall efficiency of several more percent because the motor does the braking for a longer period of time, until the wheels are nearly stopped.

Not so long ago, anyone that used a computer was assumed to be a genius, and the term "PC"-- as in "personal computer"-- had yet to be coined. It was mass production that made them so affordable that they have become more common than refrigerators. With economies of scale, a significant increase in the production of batteries for EVs and home energy storage will continue to drive down costs, and residential battery arrays will become as commonplace as refrigerators are today.

I am not worried at all by what Mr. Shanner says: he needs to remove his blinders to see the whole picture.
Posted by: Bill Dale

23.
29-Jan-2010
81176 		   Based on the following, I doubt that roof-top PV panels could provide sufficient power for the average house. I am assuming 2,000 square feet of PV panels. See whether you think that my calculations are correct and, if not, precisely where they should be changed.

According to my computations, the daily amount of power available from 2,000 square feet of PV panels is 2.64 KWH. Per the following web site, the average house uses 30,200 KWH per month, which is 30 KWH per day:

http://tonto.eia.doe.gov/ask/electricity_faqs.asp#electricity_use_home

However, I think that that’s a bit high, so I’ve used 25 KWH per day. See whether you agree with my calculations, and if not, indicate where you think they should be changed.

At high noon, the amount of solar power is about 1000 watts per square meter. Rounding, that is about 100 watts per square foot solar power at high noon.

http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-solar-energy-works.html

Assuming 2000 square feet of PV panels, that is 100 X 2000 = 200 KW peak solar power (at high noon, on a clear day).

The sun doesn’t shine for 24 hours per day, and there are cloudy days. Also, when the sun is low in the sky, less power is generated. Considering this, availability is about 20%. So, to get availability, i.e., average solar power available, we must multiply by 0.2. 200 X 0.2 = 40 KWH available (average) solar power per day.

But the efficiency of a PV panel is about 20%, so we have to multiply by 0.2 to get the average KWH generated per day. 40 X 0.2 = 8.0 KWH average electrical power per day.

Thus, with 2000 square feet of PV panels, we can expect to get an average of 8.0 KWH per day, but the average house uses about 25 KWH per day. That means that only about one third of the required power will be generated. Of course, efficiency measures could reduce the power requirements, but it would be difficult to increase efficiency enough that 2,000 square feet of PV panels would provide enough electrical power for the average house, and it could be difficult to find enough roof space for 2,000 square feet of PV panels.

Given these numbers, it would be possible to continue on to calculate the total cost of the PV panels, inverter (to convert from DC to 120 VAC 60 Hz), and the cost of the batteries to store the power for the desired length of time. As a rough guess, I’d say that the PV panels alone would cost more than $50,000 at $4.30 per peak watt for PV panels, but you can do the calculations.
Posted by: Frank Eggers

24.
29-Jan-2010
81193 		   Wow! Could you be more inaccurate on your calculation of PV power available from a 2000 ft sq rack of PV modules. You must mean a 2kw array.Not 2000 ft sq. A 200 watt module is about 15 ft sq. That's over 13 watts/ft sq or 13 x 2000 = 26,666 watts. Even using a standard derate of %23 you would still produce close to 2.6kw's in the first hour of full sunlight. Even at a low average of 4.5 equivalent sun hours/day that 2000 ft sq array would generate at least 4.5 esh x 26,666 watts x .77 = or 93kwh/day These are rough figures just off the top of my head but close enough. Most of your other assumptions and calculations are equally incorrect. I have been designing and building PV systems now for close to 20 years by the way.
Posted by: Lawrence ELLIOTT
25.
30-Jan-2010
81249 		   Let’s remember something. It took almost a hundred years to bring our electric grid, automobiles and all of our technology to the point we are today. It will take probably that amount of time to completely change over from coal and oil to more environmentally friendly fuels. And as time goes by, everything that we use will become more energy efficient and smaller and smarter. We can not be stagnant and not invest. We must look forward to the future and be able to say that we gave back to this world more than we took.
Posted by: Michael Rapp
26.
31-Jan-2010
81321 		   Michael, That would be true if America was the only industrialized country on the planet but we are now competing globally for energy resources more than ever and have very little time to make the change to green technologies.China , alone , is building a coal-fired electrical plant every 2 weeks and still manufacturing coal-fired locomotives.
Posted by: john hurt