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Solar Panels??
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Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Solar Panels?? on 01/11/2011 00:51:06 MST Print View

[solar] "it remains very effective."

In the USA, it can be effective, but not cost effective. The economic prove-in point around Palm Springs is 2-3 years. By San Francisco, it is more like 8 years. By Portland, maybe 15 years, and Seattle is maybe 25 years. There are lots of local variances, like where they get cheap hydroelectric power.

Germany may have a high rate of solar uptake simply because their conventional power is much more expensive.

Where solar power can be practical is somewhere where there is no conventional power grid. That might mean out on a backpacking trail, but it is more likely to be a hundred miles from the nearest power line in Africa.


Bradley Danyluk
(dasbin) - MLife
Yup on 01/11/2011 01:09:20 MST Print View

Yeah, I won't argue with that at all. I view the benefits of grid-independence as being the main reason to consider solar, not economics. I guess economics are the reason the uptake is so great in Germany, but my point was more that solar panels can work *technically* just dandily in northern climates irrespective of economics.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Re: Solar Panels?? on 01/11/2011 01:39:03 MST Print View


No I haven't. Here is the reason. The only way you can realize a ROI (amortize your costs over 20 years - which is what most quality companies warranty their panels for) is to take advantage of the federal and state tax credits. This means that other tax payers would have to pay for part of my installation.

It is not as simple as mounting some panels on the roof. There are many ways to do solar. Most common is a large battery bank connected to the panels and a controller in between (think voltage regulator to make it simple). Now during the day an inverter or inverters change the stored power in the batteries into 110v and 220v. As you use power from the battery bank via the inverters, any excess beyond your consumption from the panels is stored in the battery bank. If you tie into the grid, any excess electricity beyond what you use and can store is sold back to the public utility... if your local power company is willing to purchase it. At night you run off your battery bank. If the bank gets low, then you pull any needed power from the utility grid. So this means you need room to store and maintain a large battery bank and deal with inverters and other components. And of course components can break and will need replacement.

A while back I priced a 5kW system at $50,000. This will probably produce an average of 30 kWH of power per day over the year in Palm Springs. However last year my consumption averaged 33.4 kWH per day (remember we need air conditioning for several months a year). So this system will leave me short about 1244 kWH for a year. Also, panels become less efficient over time. I have not factored that in.

Last year I spent $1,800 on electricity. Assuming prices do not increase (they will), in 20 years I will spend $36,000 on electricity. The system costs $50,000 (assume I pay cash). If we assume that my total cost will be double over 20 years, then it will be $72,000. Now Ben I know you... If I gave you $50,000 today, what will it be worth in 20 years after you invest it? A lot more than $72,000!!

Of course if I let the taxpayers absorb $25,000 of the installation (moral problem for me), then the ROI is there... but I can make more than $72,000 in 20 years with the $25,000 investment anyway. Today I think Federal and Calif tax credits can net you 50% of the cost, but I have not researched it thoroughly.

However, I think in the next 5 years we are going to see improved technology and lower prices and I may then go solar on the house. The problem for the past 5 years is that with so much government subsidy in the US and Europe, demand was sky high and it kept prices high. For example the Kyocera 120w panel I bought in 2003 for $495 was going for around $700 until the last year or so. Now a similar Kyocera panel can be bought for around $400 (best deal on the Internet). Also the residential solar market is just taking off and prices will get more competitive.

A friend of mine installed solar in his house a few years ago. Much more maintenance and inconvenience than I am willing to deal with now. But that is changing quickly. Sometimes it does not pay off to be an early adapter. Do you want to by an Apple Newton? :)

The solar experiment on my trailers has been a great success, and I am just waiting for technology to get better.

Arapiles .
(Arapiles) - M

Locale: Melbourne
Re: Re: Re: Solar Panels?? on 01/11/2011 03:11:08 MST Print View

I have just installed 14 panels (about 2.5 kWh) grid-connected as part of a larger green renovation and it has been a booming success - our last electricity bill had a $148 credit. The reason is two-fold: one, we're now using nearly half the electricity we were using prior to the reno - for example, we haven't turned the aircon on so far this summer because we've found that the additional insulation is very effective at keeping the heat out, our ceiling fans are incredibly effective and the new cross-ventilation helps keep things comfortable, and because of the shaded, double-glazed north facing windows we don't use internal lights much either (and they're all CFL anyway). The other reason is that we get a net feed-in tariff (unlike Germany where there is a gross feed-in tariff) of 60 cents per kWh from our retailer. As it's high summer here now we get 8+ hours of daylight.

"A while back I priced a 5kW system at $50,000"

I'd be surprised if the system cost that now, especially because the cost of solar panels has nearly halved over the last year or so because of the Chinese factories coming on line - with RECs a 5kWh system here would be about $15,000.

Edit: I checked - about $30,000 before rebates and RECS.

"last year my consumption averaged 33.4 kWH per day (remember we need air conditioning for several months a year)"

33.4 kWh ?!!! That's nearly double what my family used in mid-summer, during school holidays, with the air-con on, when they were all at home - and you may be aware that Melbourne's a pretty warm place.

"The only way you can realize a ROI (amortize your costs over 20 years - which is what most quality companies warranty their panels for) is to take advantage of the federal and state tax credits. This means that other tax payers would have to pay for part of my installation."

Have to disagree with all that. Ultimately the reason why governments are willing to subsidise solar (or wind) is that it's no more expensive than building new power stations. So taxes can pay for new fossil fuel stations, new nuclear plants (which are REALLY expensive) or renewables. If private businesses build the power stations they will require a commercial rate of return. Distributed generation is a legitimate engineering concept.

By the way, your electricity rates look very, very cheap: both here, the UK and Japan are definitely more. I suspect that like petrol prices in the US, your energy costs are not being appropriately priced.

"However, I think in the next 5 years we are going to see improved technology and lower prices"

As I said above, when we got our quotes from our supplier the Chinese panels cost nearly half the "Australian" ones - $727 vs $1,290 (and the "Australian" ones were manufactured in China anyway). So we left the budgeted amount, added a bigger inverter and upped the number of panels. We may add a battery system as the next step.

"... Also the residential solar market is just taking off and prices will get more competitive."

As you noted re Europe, demand doesn't bring down prices - it's supply that does.

Edited by Arapiles on 01/11/2011 03:36:04 MST.

Terry Trimble
(socal-nomad) - F

Locale: North San Diego county
montbell solar charger on 01/11/2011 08:31:38 MST Print View

It to bad Montbell does not manufacture their SC17 solar charger for backpacking any more. I picked one up around 1996 and I love it. The charger is a 1.7watt multi crystalline cell developed by Kyocera that the same cells used used in power gird cells, it's mounted in resin plastic weighs 8 oz. is 4.5 inches by 6.6 inches and can charge 4 aa nicads only in 3 hours or less. This charger is developed for 700 ma AA baterrys but I have charged 900 mA with no problem and charges quickly.

I have talked to montbell usa about bring it back and revise it to charge nimh cells but they said that it is highly unlikely they would bring it back in to production .If it could charge nimh cells it would take about about 6 to 8 hours to charge a 1800 mA battery.
Here's a archived backpacker link on the solar charger.

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: Solar Panels?? on 01/11/2011 11:03:47 MST Print View

Great discussion, Nick and D W!!

Yeah, I've been intrigued with the idea of solar power for years now. But I'll wait a few more years for the reasons that Nick detailed. Right now, it's still not economically efficient here in the States. But with the combination of improved technology and competition (e.g. China) -- prices will come down. I live in Pasadena (southern Cal) and my roof is ready. :)

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Solar Panels?? on 01/11/2011 16:16:46 MST Print View

Ben, if you look at the retail price on solar panels, you can be deflated. However, there are some available at cheaper prices. Years ago, there was an early solar project out on the Mojave Desert. A year or so into the project, some problem was detected, and the whole project was dismantled. The slightly used solar panels came onto the surplus market at about 10% of the normal cost. A buddy of mine snatched up about 2kW worth and now has those installed on his house near San Jose.

Also, as is mentioned here, supposedly the Chinese-manufactured solar panels will be hitting the market with pricing substantially less than the traditional manufacturers (like Siemens).


Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Re: Re: Re: Solar Panels?? on 01/11/2011 22:26:18 MST Print View


Some great points. Your solar installation included assessment and upgrades to other items in the house. Similar to what I did with our trailer. I measured my consumption and adjusted. Biggest consumer by far was the furnace.

We use 33 kWH per day. A couple things. My HVAC system is 32 years old. We will be replacing it soon. Average high temperatures where I live:

Jan - 70F
Feb - 75F
Mar - 80F
Apr - 88F
May - 95F
Jun - 104F
Jul - 108F
Aug - 107F
Sep - 101F
Oct - 91F
Nov - 78F
Dec - 70F

In the summer, 115F is not uncommon. I have seen highs up to 125F.
I work from my home office running computer equipment 8 - 12 hours per day.
We have an electric range.

Just a FYI. US Electric Power Sources 2009:
Coal = 44.5%
Nuclear = 20.2%
Natural Gas = 23.3%
Hydroelectric = 6.8%
Petroleum = 1.0%
Other = 0.3%
Source is the US Energy Information Administration.

Also the US has huge natural gas resources and natural gas use is increasing.

I get our electricity from Southern California Edison, which is part of a publicly traded company (Edison International). Southern Calif Edison's Net Profit is 6.8% of Sales (I do not know how much power they purchase from the Government). You know my thoughts on government involvement in the economy. Lets not go there on this discussion. However, 20% of the electricity in Southern California is provided by the San Onfre Nuclear Generating Plant. Ownership of the plant is as follows:
- Southern California Edison (SCE) (78.21%)
- San Diego Gas & Electric (20%)
- The City of Riverside (1.79%)

Regarding my electric cost... I pay more than some people, as lower income users get discounts, which the higher income earners subsidize. No comment.

Regarding demand: Demand increased prices, and as supply increased to meet demand, prices began to drop.

Regarding China: If the panels are high quality, they will be cheaper than the current best products on the market. However for those who care, will Chinese produced panels create a larger manufacturing carbon imprint than other countries? Less regulation in Big Red. Pick your poison :)

Arapiles .
(Arapiles) - M

Locale: Melbourne
Re: Re: Re: Re: Re: Solar Panels?? on 01/12/2011 02:25:19 MST Print View

Hi Nick

Thanks, I call what we did a renovation, but in practice we completely rebuilt the place. Our aims were to add space (for our growing family) whilst not substantially increasing the footprint of the house, to introduce zoning, to minimise water use, to collect sufficient rainwater to keep our garden alive through extended droughts and to make the house more energy efficient (largely to shield us from the large increases in gas and electricity prices being introduced here). Melbourne has a large temperature range - about 45 C range from mid-summer to mid-winter and we wanted it to be naturally comfortable in both, instead of uncomfortable in both. We wanted to make the house solar passive but it faces the wrong way (the living areas face south - which is the wrong direction in Australia) and is made of timber and plaster, so we also needed to introduce thermal mass. And we have very noisy neighbours. And I wanted somewhere to park my bikes (although we don't have a garage or off-street parking, so I do have my priorities straight).

What we and the architects came up with was a pavillion with double-glazed north facing windows which was attached to the original house by a walkway. The pavillion has a kitchen and living room, so in the old house those rooms were converted to a bedroom and study/library. The eaves are positioned so that there is no direct sunlight on the windows from mid-November onwards but the winter sun hits the centre of the room. To get the sun in winter we had to slice off a portion of the original house's gabled roof: the new roof is angled at 21 degrees, which is the lowest the sun is here in winter. The floor is a polished white concrete slab studded with orange and black recycled glass - so it looks like terrazo, it soaks up the sun in winter and feels cool in summer. We added significant amounts of bulk and reflective insulation in the roof (about ISO r9.5 in summer - about r45 by the US measurement). We also added bulk (sound-blocking) and reflective insulation to all external walls and reflective under the floor boards. We sealed gaps to eliminate drafts. We put ceiling fans in all of the rooms and added custom-built double-glazed windows to match the period of the house. All timbers are recycled or FSC certified. Everything is low VOC. Anyway, the fans are great, we find that the temperature in the house is much more stable that it used to be and tends to be about 6 C cooler than the outside temp and we still have a decent sized backyard.

Re electricity prices - by my calculation you pay an average of about 6.7c/kWh. I just checked my last bill and we pay 19.5 c/kWh at the peak rate and 8.6 c/kWh for off-peak (NB: the Aussie dollar and US dollar are at parity, so there's no real conversion necessary). So your electricity would appear to be cheaper: from our point of view the local prices just accelerates the sense in installing PV and solar hot water.

Re the Chinese panels: the suppliers are a green business that's been around for decades. The factory in China is state of the art, a lot of the components are imported from Germany and they have the same warranties as the Australian or German panels - but obviously I can't vouch for their environmental footprint, although I think the supplier actually visited them.

And 125 F is pretty hot! On Black Saturday it was 48C in Melbourne and 49 C at my parent's farm, with a 60 k wind, so that's the hottest I have experienced.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Solar Panels?? on 01/13/2011 00:08:59 MST Print View


Wow. That's a lot of planning. Would be cool if you could post some pictures. Perhaps if we are hijacking this thread we could start a new one in Chaff.

I installed 3 ceiling fans in our living room. I have a feeling they really don't lower the temperature much, but the circulating air makes it feel cooler. Maybe I will measure it sometime.

The desert I live in usually has low humidity in the summer. If I am at home alone, I often turn off the A/C off and run a small portable evaporative (swamp) cooler in my office. Decades ago before A/C was common place, swamp coolers were the norm. I would like to install a centralized evaporative system in conjunction with the A/C system. However the venting system needs to be much bigger than A/C, because larger volumes of air must be moved. My wife nixed the idea, because she doesn't want huge vents in each room. Plus it is not as comfortable for her. Since I have lived in the desert for over 30 years, I am much more acclimated.

Actually we have a sliding electrical scale. Once you go past a baseline, rates increase.

We have 3 large windows facing south (towards the sun), and two of them are single pane. The third was a huge picture window I took out years ago and replaced with solid glass blocks. It lets light in and helps insulate. I would like to replace the other two with blocks also... that way I can't see the neighbors :) but the wife nixed that idea. So we will go with double panes. One big improvement would be to up the insulation in the attic crawl space. I can increase it easily by 4 times. Also, exhaust vents would help. We have been in the process of remodeling our house for almost 10 years. And in the next couple of years should address the efficiency of heating and cooling system. We pay as we go (cash)... no borrowing from the vampire banks. But we pay ourselves first, which means we invest/save 30% of our gross income for retirement. That is why I look at the ROI of energy improvements, and it is taking so long. Good thing she doesn't force a backpacking gear budget on me!!

Arapiles .
(Arapiles) - M

Locale: Melbourne
Re: Re: Solar Panels?? on 01/13/2011 06:09:33 MST Print View

"Wow. That's a lot of planning. Would be cool if you could post some pictures. Perhaps if we are hijacking this thread we could start a new one in Chaff."

I will post photos once the rain stops and I can take some decent photos.
Re planning, it turns out that I knew what I wanted and we found ethical, practical architects to help. There's also a green home magazine here which has won international awards because it shows homes like ours rather than mud brick or hippy places and I got a lot of ideas from that.

"I installed 3 ceiling fans in our living room. I have a feeling they really don't lower the temperature much, but the circulating air makes it feel cooler. Maybe I will measure it sometime."

That's right, they don't lower the temperature - but because they're moving air over your skin they do cool you down. We have them over our bed and my wife's taken to sleeping under a doona, even when the rooms about 25C. My 2 year old was sleeping under one the other day and her skin, where it was exposed, felt almost cold.

Kendall Clement
(socalpacker) - MLife

Locale: Southern California
Re: Solar Panels?? on 01/13/2011 13:24:08 MST Print View

Mark Ryan,

I just got my Solio Classic that I bought in Gear Swap for $40. I'm excited and I can't wait to try it out. I'll post on this thread my experience with it the first chance I get to use it.


Edited by socalpacker on 01/13/2011 18:01:47 MST.

stephan q
(khumbukat) - F
re: "Solar Panels" on 02/16/2011 22:03:01 MST Print View

We rely on AA eneloops and solar power while traveling. 2 for the camera, 2 for two zebralights, and two in the charger, for total 6 on board. Batteries are cycled before fully discharged, this way we are" topping them off" instead of trying to "recharge". Our last system was powerfilm based, and was ok. In search of more power, found a thread on WB that got me started.
This is my current mock-up. 3.0 oz. total. Based on this Kyocera mini module rated at 1.4 watts.

Specifications Wired for 6V Wired for 12V
Rated Power (Watts)
1.4 W
Current at Max. Power (mA) 182 mA 91 mA
Voltage at Max. Power (Volts) 8 V 16 V
Short Circuit Current (mA) 190 mA 94 mA
Open Circuit Voltage 10.7 V 20.0 V
Length 6.02 (153mm)
4.64" (118mm)
.16" (4mm)
0.20 lbsk minik mini rear

Currently using 1n914 diode, which draws 1 volt. My technical questions include...Is this correct diode? And if not, what would be the proper diode for this application? Does this unit produce enough power for charging 4 AA's in short order? We are thinking of adding a Steripen Classic to the mix.

This mock-up raised tired batteries measured 1.1 volt, to fully charged at 1.35 volts in about 4 hours of winter sun, at 37.9N latitude last week. This seems good to me, but is there something I could change to increase charging power?



Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: re: "Solar Panels" on 02/16/2011 22:58:29 MST Print View

You say that you are currently using a 1N914 diode. What for? Are you using it as a blocking diode? That would be used to insure that charged battery power is not fed backwards to heat up the solar panel, which would be wasted power. The forward voltage drop across the diode will be closer to 0.5 or 0.7, although there are some diodes with less forward voltage drop.

Your batteries are probably rated for a full charge output of about 2000 mAH each. One general rule of thumb is that you charge a battery at 1/10 of the full charge output, and you charge it for ten times the time, which would be ten hours in this case. Other batteries can be fast-charged, but let's start with the rule of thumb. You seem to be charging the batteries two at a time, so you need enough voltage to drive in 200 mA, and that is into two (1.2v) cells in series, so you need more than 3 volts to do it. You seem to be getting 6 volts out of the solar panel minus a half volt lost in the diode, so that might be sufficient. On the other hand, 6 volts might be significantly high, which might drive significantly more than 200 mA into the batteries, if that were available at the solar panel. I'm guessing that there won't be high current since your data shows 190 mA maximum at short circuit condition. Basically, if you want to speed up the solar charging process, you could double the size of your solar array and double the current available to the batteries.


stephan q
(khumbukat) - F
Solar panel diode on 02/17/2011 13:15:20 MST Print View


Yes, I'm using the diode for blocking reverse flow. I guess my question revolves around my lack of understanding regarding this diode. I know the voltage drops through the diode, but does the current drop as well? Next sunny day, I will use my multi meter and do some tests. Trying to find best diode that blocks reverse flow and allows maximum charging from one module. Thanks for your help.


jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Solar panel diode on 02/17/2011 13:51:56 MST Print View

I charge a battery without blocking diode

Different application - 9 V lead acid battery - but should be the same for small battery

If you remove charger from battery at night, you don't need blocking diode

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Solar panel diode on 02/17/2011 14:26:39 MST Print View

Jerry is correct that he probably doesn't need a blocking diode. On the other hand, it may or may not hurt much.

Think of a diode this way. It lets the current flow in the forward direction, and it does not limit that. Also, assume that there is a slight voltage drop across the diode that way, usually about 0.5 to 0.7 volt. And the current cannot flow back in the reverse direction. That 0.5 to 0.7 volt is relatively insignificant when you are charging with a big solar panel (with an open circuit voltage of 16 or 17 volts). However, when you get down into low voltage panels like 6 volts, we are talking about a diode drop of about 10% of the solar panel voltage. So, Jerry may have been trying to avoid that.

Current really does not or cannot drop through the diode. However, the current might drop slightly because of the diode's forward voltage drop.

Yes, you can learn some things about your solar system with the use of a multimeter. You will probably get the most result from orienting your panel toward the sun and avoiding any shadows across the panel.

As your current starts to rise, you will get some good out of using slightly heavier gauge copper wires to carry it. But, as long as your current stays down around 200 mA, it doesn't make too much difference. I used a lot of 10 gauge copper on my home installation.


Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Solar panel diode on 02/17/2011 14:36:37 MST Print View

Hi Stephan

Bob is right that you do not HAVE to use a blocking diode, but it is generally considered good practice - and a sensible move. It prevents problems when you forget to unhook the charger immediately. Which happens ...

You can reduce the forward voltage loss by substituting a Schottky Diode for the 1N 914. It has a lower forward voltage drop, but is a bit more expensive. Make sure you select one with an adequate current rating. 1 A units seems to be readily available.

No, the current will not really drop much with the diode in place: think of it as a backflow valve on a hose.

Solar cells are funny beasts. They can handle the voltage drop due to a blocking diode with very little trouble. They are really limited in terms of current output: they usually have gallons of voltage capacity. Best to think of them as having a current output controlled by the amount of sunlight input.

PS: I use a solar charger at times too.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Solar panel diode on 02/17/2011 15:08:45 MST Print View

Yes, the Schottky Diode is a little bit of overkill for a low power backpack panel, but you could probably measure the improvement. It could get more important for a higher current lower voltage panel. In my home system, I might have more than 5 amperes flowing for years, so it is nice to get rid of little losses, which is why my charge controller has Schottky Diodes inside and ordinary blocking diodes at the panel. Single crystal solar panels will generally give you a higher open circuit voltage than the amorphous solar panels.


Jeremy Malin
(jrmalin) - F

Locale: New England
Re: Solar Panels on 02/23/2011 07:22:42 MST Print View

Been reading for awhile and finally decided that I needed to join and take part. I know that this thread is a few days old, but I did want to add a few things. If anyone is looking for a ready to use solar panel charging option, take a look at the GoalZero products. They seem to be pretty well regarded amongst the photography community and have a wide range of options (maybe even light enough for the BPL community).