Can Solar Energy Reduce High Electricity Costs in California's Central Valley?

[Chi Meson]

We do have a south sloping roof, not sure about the pitch though. We only get freezing temperatures a few times a year. Though that sounds like a lot of maintenance for my parents to handle.

The maintenance for the in line tubes is bar far the least maintenance for any system, whether thermal or PV. Here's the link for the tubes I was http://www.sunmaxxsolar.com/evacuated-tube-solar-collectors.php".

If there is a regular month when all the freezing occurs, then the tubes should be left drained during that time. The procedure would be no more than turning two valve levers and opening a drain. To get it back on line, close the drain, and turn the two levers again.

Pets are much more laborious than that.

 

[Ivan Seeking]

Something else, you may find that geothermal heat pumps or a/c units can compete with solar, in your area. I don't know the track record of these systems yet [just happen to be revisiting that issue lately] but in principle they can improve the efficiency [not really, but effectively so] of your a/c unit by I think about 200% [according to the sales info...]. They do this by using the relatively cool Earth on your property as a heat sink, rather than using an air-cooled condenser. By doing this, your ac unit has do less work for the same cooling capacity.

I would bet that these systems are at least competitive with solar, if not more. I don't yet know if they have delivered as promised, but they have been around long enough now to evaluate their success.

 

[Pengwuino]

You need to determine the typical output per sq meter for your area based on real examples, the cost per unit area for the pv panels, the cost of power from PGE, the cost of the installation per sq meter of panel [including all PGE-related work], the life of the panels, and from that determine the minimum sized system that is profitable. There is some minimum size below which you will never see the pay back. Generally, you are looking at 10-15 years for a good or ideal system. Once you get into 20 and 30 year return cycles, you are into the life of the panel, and its a net zero gain.

I can tell you that I was looking to put in low-head hydro on my property. Just to get feedback protection, I needed to buy a $10,000 switch. How long would it take to pay for just the switch with my 5KW hydro, at 12 cents per KWHr?

I think we'd end up having to get someone out here to figure everything out but I bet the prospects are good considering our steep roof, ridiculous costs to buy power, incentives, and the fact that I think Fresno is an hours drive from the Sun.

One thing I wonder, on a separate but related issue, is how do people make businesses out of selling solar power? I saw PG&E's contract rates at about $.10/kwh for solar power. Do you just get huge economy of scale cost reductions? I suppose it's a question of whether or not the installation costs scale linearly with the power output...

 

[Ivan Seeking]

I think we'd end up having to get someone out here to figure everything out but I bet the prospects are good considering our steep roof, ridiculous costs to buy power, incentives, and the fact that I think Fresno is an hours drive from the Sun.

But not a salesman. Also, you really need to see proof of the average annual output per unit area of panel, for your area. Keep in mind also that your installation cost will not vary linearly with the size of the installation. It will be more of a step-wise function at the low end, with a minimum cost no matter how big the installation.

One thing I wonder, on a separate but related issue, is how do people make businesses out of selling solar power?

Who says they do? AFAIK, solar is only now competitive at the user level for solar-friendly areas. If there are any examples of commercial production sites that are competitive, they were surely funded with grant money that doesn't have to be paid back.

 

[Pengwuino]

But not a salesman. Also, you really need to see proof of the average annual output per unit area of panel, for your area. Keep in mind also that your installation cost will not vary linearly with the size of the installation. It will be more of a step-wise function at the low end, with a minimum cost no matter how big the installation.

Aha! Thats where the fisicist in me comes out! I was thinking of figuring out the equipment needed to put a small single panel up on the roof and monitor the actual intensity that we can get throughout the day. Step 2: Extrapolate. Step 3: Profit! Or not.

Who says they do? AFAIK, solar is only now competitive at the user level for solar-friendly areas. If there are any examples of commercial production sites that are competitive, they were surely funded with grant money that doesn't have to be paid back.

Pff, I thought I smelt something fishy. I was thinking the only way it would make sense is if the costs of expanding from say, a 100kW to a 200kW system were mainly in the panels and possibly meant economies of scale were important. I really don't know how the costs of running these things are spread out equipment wise.

 

[Ivan Seeking]

Aha! Thats where the fisicist in me comes out! I was thinking of figuring out the equipment needed to put a small single panel up on the roof and monitor the actual intensity that we can get throughout the day. Step 2: Extrapolate. Step 3: Profit! Or not.

You really have to be careful at the low end. That's where the initial costs can kill the whole deal. Size does matter... even in California.

Pff, I thought I smelt something fishy. I was thinking the only way it would make sense is if the costs of expanding from say, a 100kW to a 200kW system were mainly in the panels and possibly meant economies of scale were important. I really don't know how the costs of running these things are spread out equipment wise.

You do get the economy of scale, but this only goes so far, and then you run into distribution costs.

What example did you have in mind?

 

[Ivan Seeking]

I would bet that you could safely use {$10K <= cost}, as a starting point for the electrical system needed to make it PGE safe...not including the cost of the electrician. As I said, this was my out-of-pocket cost for one switch that I was required to buy - independent of the size of my alternative power source. Phase and voltage concerns were still my problem [and cost].

Then again, with all of the emphasis on solar in your state, the minimum size issue might have improved siginficantly. Maybe it won't be that bad anymore.

 

[mugaliens]

How is that different from smart metering? That is how smart [net] metering works.

Otherwise, you have to dedicate loads to the panels, which becomes problematic.

My uncle runs a smart meter which records both gain and loss from his solar power panels, as well as the net, for which he is either billed or paid. Spring and Fall he makes money. In winter he looses a little bit, and during the summer it's a bit more, although his design (he designed and built his home) covets an insulated basement and R-50 walls with an R-75 ceiling. He's done some additional improvements since then involving aluminized mylar reflectors, so I think that while the insulation factors remain the same, the amount of heat entering the home during the summer has been cut by about 75%, while the amount of heat gained during the winter has increased several hundred percent. Even though he lives in Michigan, I don't think he even has a heating bill anymore. I do know he installed a thermal-salt storage system which leverages what he collects during sunny days to take care of those cold winter nights and cloudy days. It's a phase-change system, not a molten system. His only complaint is that after a few years "things grow and get nasty" in his words, but as the salt solution just sits there and is totally enclosed, he really doesn't care.

I asked him once why he didn't simply go with a water system and he told me that much less grows in the salt than would in the water, and the chemicals used to treat the water would be very expensive, while the brine of the salt keeps most things at bay without having to treat anything.

A few years back he had a problem with his solar panels during the summer, as simply turning them off would cause the water to boil, so he had to drain them in the Spring and refill them in the Fall, but from what I understand, he has since built a "summer shunt" in which they're simply routed to an outside radiator, which keeps the system below boiling point. It's passive, so no electricity is used, and he still taps the system for hot water. During the winter he does drain the external radiator cycle, but not until around November. He starts using it again around April.

 

[Ivan Seeking]

Just out of curiosity, I checked on one scenario to see how it works out at today’s prices.

I am seeing a price of about $400 for 75 watts, for solar panels.
http://www.affordable-solar.com/bp-solar-bp-375J-75-watt-solar-panel.htm

If we want to run a 1000 watt auxiliary air conditioner unit that is isolated from PGE, we probably want to allow for at least a 50% fudge factor [0.707 multiplier against the output capacity of the panels, to allow for the angle of the sun] so that the unit will function through a good part of the day, so figure 1500 watts. This requires 20, 4x2 [ft] panels, at about $8000, and having a footprint of about 160 square feet.

Add the ac unit for about $500, so $8500, plus the installation of the panels. Assume that you do all of the work at a very low cost; so we’ll say $9000. [technically, you still need a $500 inverter]

At 40c/KW-Hr, and generously assuming that we get operation 8 hrs a day in the summer, it would take about 2800 summer days [maybe 28 years or so] to pay for the installation. Assuming that you can get 4 hrs of power per day in the late spring and early fall, maybe one could double the annual yield and see a profit in 14 years. In the winter you probably couldn’t generate the power required to run the a/c unit, but you might run a 500 watt heater for part of the day. So you might see payback in a little over ten years or so. But the 8 hour per day number is likely way too optimistic using a 50% overcapacity, even in your area.

This is where the grid is handy. You can use everything that you produce. It functions as an infinitely variable load. But to do that, you probably need to tack another $10K onto your installation price, so now we are looking at 20 years to break even. The way to improve that number is to put in more panels. .

 

[mheslep]

Just out of curiosity, I checked on one scenario to see how it works out at today’s prices.

I am seeing a price of about $400 for 75 watts, for solar panels.
http://www.affordable-solar.com/bp-solar-bp-375J-75-watt-solar-panel.htm

Not that it effects your narrative aside from payback time, but that's fairly old and expensive technology at $5.3 per Watt (and made Beyond Petroleum). Here's a newer example at $3 per Watt, same website, different make:
http://www.affordable-solar.com/sharp-ND-U224C1-224-watt-solar-panel.htm
which will also require 30% less area and mounting infrastructure for the same total power installed.

 

[Ivan Seeking]

Not that it effects your narrative aside from payback time, but that's fairly old and expensive technology at $5.3 per Watt (and made Beyond Petroleum). Here's a newer example at $3 per Watt, same website, different make:
http://www.affordable-solar.com/sharp-ND-U224C1-224-watt-solar-panel.htm
which will also require 30% less area and mounting infrastructure for the same total power installed.

Interesting, I checked the top three google hits, which were all landing at ~ the same price.
http://www.google.com/search?source...=UTF-8&rlz=1T4DGUS_enUS313US313&q=solar+panel

The 8 hours per day is likely about 20% too high for a 50% overcapacity, but the price drop is encouraging to see.

 

[mugaliens]

(sigh) Install IR reflectives in your attick then open a window when it gets hot.

What's this four hundred dollar stuff? Marketing hype? Someone in the business is definitely stringing you along!

Try $40. Yes - "fourty."

 

[Ivan Seeking]

(sigh) Install IR reflectives in your attick then open a window when it gets hot.

I've seen it 125 degrees F at the north end of the Sacramento Valley [same valley where Pengwuino lives]. 110-degree days are common. IR reflectors and open windows won't cut it.

I remember it being 80-90 degrees at midnight, many times.

 

[Pengwuino]

I've seen it 125 degrees F at the north end of the Sacramento Valley [same valley where Pengwuino lives]. 110-degree days are common. IR reflectors and open windows won't cut it.

I remember it being 80-90 degrees at midnight, many times.

Yup, its a god awful area to live. Climate-wise, it's actually considered a desert.

 

[Ivan Seeking]

Yup, its a god awful area to live. Climate-wise, it's actually considered a desert.

Remember that terrible heat wave three years ago? At the time, I was working in a plastics plant in the sacramento area, that was running over a million watts of heat inside the plant, which was not climate controlled. I would bet that it was over 130 degrees in there on the worst afternoons.

The hotel a/c was a large, common [freon] system, that failed. So everyone in the hotel lost a/c. People were actually sleeping in the pool on rafts!

 

[Pengwuino]

Remember that terrible heat wave three years ago? At the time, I was working in a plastics plant in the sacramento area, that was running over a million watts of heat inside the plant, which was not climate controlled. I would bet that it was over 130 degrees in there on the worst afternoons.

The hotel a/c was a large, common system, that failed. So everyone in the hotel lost a/c. People were actually sleeping in the pool on rafts!

Yup, our a/c couldn't handle it. I couldn't be upstairs where my computers are until around midnight those days because the monitors wouldn't run at the temperatures the room was at. We had our pool up those days and you'd get out, dry off, and boom, instantly sweating.

 

[Ivan Seeking]

The http://library.thinkquest.org/20331/types/solar/problems.html.

My brother in law had this installed while I was there this month:

To the right are solar heat exchangers to heat water boilers, to the left are 16 solar electric panels. The lattitude of the building is about 43 degrees north, so you can do your calculations and he was told that the installation would be good for an average of 3000 watt, the legal maximum for private grants in France.

As soon as the installation was operational, a week or so ago, we observed the indicator giving a maximum momentarily yield of 1950W indicated on a bright day at noon, and about 400W maximum on a very dim rainy day. He was not very satisfied with that.

The heat exchangers meanwhile heated the warm water reservoirs to around 70C.

What is the electical load being driven by the solars panels? If you don't have a 3000 watt load, you can't produce 3000 watts.

 

[mugaliens]

I've seen it 125 degrees F at the north end of the Sacramento Valley [same valley where Pengwuino lives]. 110-degree days are common. IR reflectors and open windows won't cut it.

I remember it being 80-90 degrees at midnight, many times.

I hear you. I used to live in Vegas, where it sometimes remained above 100 throughought the night, and you're right - active air conditioning is about the only way to go.

 

[mheslep]

Interesting, I checked the top three google hits, which were all landing at ~ the same price.
http://www.google.com/search?source...=UTF-8&rlz=1T4DGUS_enUS313US313&q=solar+panel

I suspect, from indirect observation, that those low power panels come from old inventory which can be moved because there continues to be a market of buyers for the just-one-panel-at-100W, enabled by the internet, in which case $3-400 beats $680/220W every time.

The 8 hours per day is likely about 20% too high for a 50% overcapacity, but the price drop is encouraging to see.

The price could be said to be collapsing in the last couple years:

http://www.technologyreview.com/energy/24498

According to Harry Fleming, the CEO of Acro Energy Technologies in Oakdale, CA, these changes mean that the cost of a typical five-kilowatt rooftop solar system has dropped from $22,000 after state incentives are applied ($40,000 without them) to $16,000 in the last 18 months. Prices are expected to fall to $13,000 by the end of the year ($25,000 without incentives). "This is going to make solar a middle-class product," he says

With incentives that's $2.6/W installed.
Also see this history from some people in the business since the 70's
http://1366tech.com/v2/company-mainmenu-1

 

[mheslep]

Yup, its a god awful area to live. Climate-wise, it's actually considered a desert.

Ouch, that will ding the solar panel efficiency, maybe 15% less than at room temperature. That is, a 5KW array would put out only 4.2KW at 140F panel surface temperature vs 72F.
http://www.solarpower2day.net/images/9t.png

 

[Ivan Seeking]

Ouch, that will ding the solar panel efficiency, maybe 15% less than at room temperature. That is, a 5KW array would put out only 4.2KW at 140F panel surface temperature vs 72F.
http://www.solarpower2day.net/images/9t.png

Just mount them in the shade, duh!

 

[Ivan Seeking]

Someone should incorporate hot water preheater tubes into the panels, for cooling. You reduce the load on your water heater and have more efficient panels, in one stroke.

 

[Pengwuino]

Someone should incorporate hot water preheater tubes into the panels, for cooling. You reduce the load on your water heater and have more efficient panels, in one stroke.

Water + Electricity, always a good prospect

I do like the idea of combining technologies though, that is smart. Fact of the matter is it almost seems silly when it's summer time and you want to make food and you DON'T rely on the fact that the suns cooking your house to help cook your food.

 

[Ivan Seeking]

Water + Electricity, always a good prospect

It depends on the electrical layout. I'm not sure if these are normally run in series and parallel to achieve operational voltages, or if they keep the panels at 12 or 24 volts [for small systems], and only step it up at the inverter. Maybe mheslep knows. But it wouldn't need to be intrinsically dangerous. Ideally, I guess, it would probably be a matter of heat-sinking capillaries that carry water, embedded in the construction of the cell. I don't know if there is any practical way to retrofit something to existing panels.

I do like the idea of combining technologies though, that is smart. Fact of the matter is it almost seems silly when it's summer time and you want to make food and you DON'T rely on the fact that the suns cooking your house to help cook your food.

Given that one might get a 10% efficiency gain in the pv alone, one would think it would be cost justified. And most of the energy that hits the panel still goes to heat.

 

[mugaliens]

If I ever install a solar electric production unit, it'll be a http://en.wikipedia.org/wiki/File:EuroDishSBP_front.jpg" unit, not photovoltaics.

Lower lifetime $/kW-hr.

 

[mheslep]

The Electrical Code recommends parallel combinations of series chained panels to reach 24 or 48 VDC, depending on the controller/inverter. See, e.g. figure E-6 here:
www.senecass.com/NEC2000.pdf

 

[mheslep]

If I ever install a solar electric production unit, it'll be a http://en.wikipedia.org/wiki/File:EuroDishSBP_front.jpg" unit, not photovoltaics.

Lower lifetime $/kW-hr.

Really? That presumes a lot of disposable yard area at your residence. Do you have a source for cost?

 

[Astronuc]

"Power bills for the most energy efficient of the three houses totaled less than $450 for the entire year," Project Manager David Dinse said. "That averages out to about $37 per month for a three-bedroom, two-and-a-half-bath house."

http://www.prnewswire.com/news-rele...e-first-year-of-energy-savings-100136039.html

Of course that's in Tennessee, not CA.

But there might be some good ideas there.


Have you tried a giant beach umbrella?

Really what the house needs is shade.

Does the house currently have a ridge vent?

 

[Ivan Seeking]

The Electrical Code recommends parallel combinations of series chained of panels to reach 24 or 48 VDC, depending on the controller/inverter. See, e.g. figure E-6 here:
www.senecass.com/NEC2000.pdf

I didn't think they would want people putting 120 or 240 VDC on their roofs - very dangerous stuff! But at 24 volts, it would be all but impossible for the water to be a problem, even in the event of a failure. Many trucks run 24 volt systems. Operators and mechanics sometimes use pressure washers on the batteries.

On the other hand, we had a guy take a pressure washer to a live, 480 VAC [three phase], open panel, in North Carolina. : He is lucky to be alive.

 

[Ivan Seeking]

A bit off-topic, but for anyone interested: I spent a fair amount of time playing with the idea of "smart loads", in order to maximize the efficiency of my 5KW_max, low-head hydro project. Note that hydro runs continuously, 24 hours a day - quite a bit more practical than solar! But the key to maximizing the efficiency of any alternative power system is to match the load to the supply. In order to do this, one needs loads that can be varied according to some key operating parameter; in this case, the generator/turbine speed.

In order to avoid the $10K switch for a PGE tie-in and the associated hazards, I made plans to run an isolated system with variable loads. By fixing the turbine to the ideal speed [for the associated head] the loads would effectively vary according to the rate of water flow in the creek at any time. In the end I scrubbed the project because the creek simply moves too much rock [large rocks!] - the anticipated maintenance needs made it impractical. But that realization only set in after I had layed out the entire project, and it all looked pretty good.

Through a combination of tactics, I managed to find ways to always match the supply with a load. PWM control of the central heating elements for the house, and variable-speed fan control, were key concepts [actually, I think this was later simplified to some level of discrete control because the heating elements were 2500 watts]. The heater could be switched from aux to line power at will. Also required was a large, auxilary water heater, to be used as a hot water pre-heater and as a secondary variable load. This was a completely dedicated system that never used line power. It appeared that with these and a few other tricks [like heating my office with an small aux heater], I could untilize ~100% of the available power for the duration of the annual life of the creek - about 8 months out of the year. We have no signifcant flow in the summer, but our energy requirements drop dramatically over the summer. We use very little a/c here.

It really broke my heart when I had to can that one. It would have been fun.

The point: I think "smart loads" could still be a useful idea.

For any hydro fans, I had designed a Banki crossflow turbine for the flow and head range. The required equations and plans for these turbines [the plans that I worked from] can still be found in an old paper from Oregon State University.