Lloyd’s roof-mounted solar panels (image via Extreme Tech)
In response to a Slashdot / Extreme Tech article about a $60,000 residential PV system that still leaves its owner with $200 per month winter power bills, Mikey Sklar posted the following tips:
1. Roof Mounted Panels Suck – They often have limited or no tilt
control and clumsy to maintain. This means that you will likely get
strong performance in summer or winter, but not both. Finding the
average latitude tilt for your region and mounting the panels at that
angle is your best option for roof mount. Trackers can bring your
performance up by 1/3rd, but will include extra expense and
complexity. Consider a manual tracking system which you just push with
your hands through out the day if you need a early morning or late
afternoon boost. This is ideal for the off-grid / unemployed eco-geek.
2. Grid Tie has issues too – Although grid-tie allows a PV install to
greatly reduce their installation time and costs they also have some
drawbacks. Continuing to buy power from a power company can result in
relatively high monthly fees if the system purchased was undersized.
Many grid-tie installations have no battery backup so when the grid
dies, you lose all your juice too. In remote towns many power
companies only pay the customer a 1/4 of what they charge the customer
for power. My town being unusually behind the times refuses to
purchase any power from their customers.
3. PV Batteries – New batteries are easy, but old ones can be fixed.
Our world is hemoraging so called “dead cycle batteries”. Try talking
to your local golf course, marina, or auto parts store. As you learn
to test cells and repair lead acid batteries through desulfation you
can save yourself a fortune in batteries and store large amounts of
energy. Keep in mind that batteries are much like people. They like
72F temperatures and a little exercise. Do not cycle the batteries
below 50% on a regular basis. I try to stay over 70% capacity on my
battery array at all times.
4. Heat – My panels tend to have a pretty big drop off in performance
during the summer. This is partly due to my not adjusting the PV array
to be almost flat during June. It is also related to our monsoon
season bringing in lots of rain and cloudy weather. However, the real
killer of performance is the temperature. High temperatures drop my
panel performance by 30%. Our temps in June sit peak around 100F in
June which is enough to dramatically reduce the performance on a
polycrystal PV cells. The monocrystal cells are supposed to handle the
higher temperatures better.
Thanks Mikey (and Lloyd!)
8 thoughts on “Solar energy: some tips”
The system cost $36k to install, not $60k (read your link). And though he had $200 electric bills, this was down from $450. A little fun with time-valuing the saving has it at a 25-year pay-back for a 7.5% discount factor.
Also notable, the cells are single crystalline, not poly so the cells should operate well in the summer (in fact Sunpower cells are starting to get used in 10x concentrator applications albeit with beefed up contacts). Sunpower charges a premium (on a power output basis) for the highest efficiency cells, he admits he could have gotten by cheaper.
Panel prices have fallen ~30% in the last 6 months, so solar is becoming an increasingly good way to save money BEFORE you count for the real energy costs of using electricity from coal.
I think I’ve been wasteful if my electric bill goes beyond $70 a month, and I don’t have a PV system.
Of course, I don’t have a house full of media-addicted people (family), multi big-screen HDTV sets, extensive architectural/landscape lighting, spa/swimming pool, Viking freezer, etc., nor do I have a cluster of PC’s “benchmarking” their little hearts out 24/7.
Still, a 50% reduction in expense from one year previously is nothing to sneer at, any way you look at it. I haven’t been able to effect that kind of savings since I went CFL and dropped the monthly bill from $49 to $27.
These panels are on a very poor angle (unless this guy lives in the tropics).
Also, PV panels are not worth the cost if you have access to a power grid. They typically take 25-30 years to pay for themselves assuming zero maintenance expenses. This is pretty unrealistic considering the finite life span of the roof itself.
On top of that, the environmental impact in manufacturing these things is far worse than just using the power grid if you have access to it. In rural areas with no power, this can be a less expensive way to go in terms of dollars. In mobile applications where wires would not be practical, this is also a good way to go.
Solar *heating* panels on the other hand make a lot of sense in areas with a good amount of sun. I can’t imagine what this guy was doing for $450 a month in electricity, but solar heating panels can slash your heating bill 80% or more.
Thank you for the great article and the pictures. I personally live in an apartment, so i don’t get a chance to switch to Solar energy, but I’d love to. I have an article, called the future of solar energy and it’s bright, the future is. I believe that soon people will think of buying solar panels more, than they do now. Some of them will hopefully follow your example.
My ecology and environment blog
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