How to make a solar home ?

Our government is about to double electricity bills soon due to the recent increase in fuel prices so i was wondering if solar power alone could be enough to power a home all year round ( or at least drastically reduce the electricity bill ). Malta is a sunny place practically all year round except for a couple of months when it is a bit gloomy.

I have no experience in large scale solar power so im going to need all the info, pros and cons i can get.

I do not keep track of the latest solar technology and i dont know if the technology has developed enough to make this a practical solution but anyways i would like to explore this in detail with the solar veterans here.

In Malta we do not have the option to sell electricity back to the grid so i guess a battery bank would be needed to store the produced electricity and used when needed and some kind of automatic switch that switches to and from the power grid when the batteries are empty/ready to use as i guess it would be prohibitively expensive to completely rely on solar power.

while browsing i have seen many types/chemistries of solar panels. what is the difference between all of these types, which would be the best 'bang for the buck' and how many of them are needed ?

In Malta we use 240V 50Hz electricity does that mean that im going to need 20x12V batteries or does the inverter boost the voltage as required ?

what kind of batteries suit this project best and how long would they last before needing replacement ?

from the little i have seen 3 main parts are required - the solar panels, the batteries and the inverter. is there anything else needed ?

i dont know the exact amount but we probably consume an avrage of about 800 Watts/hour but im sure we could bring that down to about 500 Watts/hour. what size of system would that require ?

and finally what will it cost ? ( and cheapest place to buy them )

I know too many questions but if someone could find the time to answer them i would be very grateful.

Thanks a lot

Mike

Amonra said:

from the little i have seen 3 main parts are required - the solar panels, the batteries and the inverter. is there anything else needed ?

i dont know the exact amount but we probably consume an avrage of about 800 Watts/hour but im sure we could bring that down to about 500 Watts/hour. what size of system would that require ?


Mike

Click to expand...

Hey Mike.

You can build a system that is pretty self sufficient. Typically, the battery banks are 48 volt or lower. The solar panels will genrate a different voltage throughout the day, so the charger takes that (sometimes a couple hundred volts) and steps it down to what the batteries need. The charger is often built into the inverter.

Your average 800 watts per hour means you use 19 kwh (kilowatt hours) per day. You can devide that by the voltage to see how man amphours you need. 19,000 kwh / 48v = 400 amphours. But you don't want to discarge your batteries too far, or they break down too soon, so assume you need 800 ah at 48 volts and you'll stop using them when 50% discharged.

Make sure that you verify what your peak needs are, not just your average. You may find the microwave pulls 1200 watts all by itself.

As you can probably tell by now, it's quite doable.

You'll also need an automatic transfer switch to put you on grid power when the battery voltage drops. That might or might not be part of the inverter.

DO a googe search for "hompower" to find resources like
http://groups.google.com/group/alt.energy.homepower/threads?gvc=2

Good luck,

Daniel

Here is a quote from this site:

http://www.e-marine-inc.com/products/solar_panels/solar_panel.html

"What type panel is best? There are three main types of solar panels: Monocrystalline (Siemens), Polycrystalline (Kyocera, Solarex, PowerValue), and Thin Film or amorphous (Uni-Solar). Monocrystalline panels have uniform dark gray cells and have the highest output per cell area and tend to be the most expensive. Polycrystalline cells look somewhat like shattered glass and tend to be less expensive and only slightly less efficient per cell area. These cells are usually square and result in a slightly smaller solar panel than solar panels constructed using the more efficient monocrystalline which tend to be rounder. Monocrystalline and polycrysalline solar panels are rigid and have a glass cover. Thin Film type panels are made by depositing the active silicon on either a stainles plate or a flexible backing. Thin film type panels are about half as efficient per cell area but are consided unbreakable and shadow protected. "

And another quote from this site:

http://www.personal.psu.edu/users/c/x/cxo163/html/solar.html

"Grid-tie" Solar Systems

A "Grid-tie" solar system is useful for homes that are already connected to the utility grid. The advantage of this type of system is the price reduction of utility. The system has to be wired with an inverter that produces pure-sine-wave AC electricity, which is necessary for connecting to the utility grid. Another advantage to this type of system are the tax incentives and rebates available from different state and local agencies. Owning a grid-tied system in California qualifies you for the State Buydown program, drastically reducing the overall system cost. Most of these systems typically do not have the battery storage that allows for power when the utility fails. Grid-tie system can be installed with battery backup power to keep critical loads operating in the event of a power failure."

The internet is LOADED with good information on solar energy.

A good book is "Got Sun? Go Solar"

http://www.countrysidemag.com/books/gsgs.htm

There is a magazine called Home Power that has been out for many years. They have a website at: http://www.homepower.com/

I would look for their magazine since it has a lot of advertisement for the components you will need.
oleblue

Amonra,

I started a thread on How to Sell Electric Vehicle/Solar Power?

It is long, but near the front there are some web sites that list options, costs, and expected power from various types of systems... And towards the end we talk about the expenses of replacing old appliances vs the costs of running them.

In the US, a Grid-Tie 3 kW (peak power) system costs about $30,000 (list prices, professionally installed with permits). A very basic Battery backed system would cost ~20% more (this was for something like a 10 kWhr battery pack--you could price additional batteries for your needs). Here in the US, a battery based system would probably cost you, approximately $0.25 per kWhr. As always, if you can get good prices and do all of the work yourself, you may be able to cut your costs almost in 1/2.

For me, near San Francisco in Mid September, I can get about 15 kWhr's per day (decent roof pitch, close to pointing south, some tree blocking around now and into winter). With Batteries, you may get 20% less because of battery/system losses (+/- rough guess). In Summer I will get much more (Better than 19+ kWhrs???). Winter will be less (don't know yet). This for a 20 panel BP 4175B (175 watts per panel) Grid Tie system. My system should do better than 48,000 kWhrs a year on average... Over thirty years, you will lose ~20% capacity due to panel degradation by the sun.

Darell probably can give you a better estimate as his system is several years old (whereas mine is only a month or so)...

If you have a tracking panel (always points at the sun through day/seasons) you can get, roughly twice as many kWhrs in a day (or use 1/2 the panels). Tracking seems like it should be very cost effective--but it seems the mechanics for the tracking motors needs a lot of service over the years (even one Solar Store in California has them, but most are not working now--only the fixed type arrays seem to be maintained).

My humble suggestions:

Get your power usage down as much as possible first. Use fluorescent lights and screw-in CFL's (get rid as many incandescent bulbs as you can), replace old inefficient appliances (air conditioners, refrigerators, freezers, washer, dryer, etc.).

Once you have reduced your power as much as practical for you--then you can size your solar array for your needs.

If you live in a windy area and have the room (and your neighbors are not too close), you can also think about using a windmill to produce power. They can be a bit noisy, and need more service, but are also a good alternative/supplement.

Are there any solar installers/importers in your area? Europe has, very good (if not better) than the US, options for solar/wind companies...

Of course, your prices and options will depend on what is available to you in your country... And, what taxes (and tax rebates--if any) will do too...

Do you have any manufacturers and/or prices for basic panels, inverters, and storage batteries for your area? Any special requirements (building codes, places where you can install the panels, etc.)?

You really need to put some pretty exact numbers together for your system (how much panel space, what does power cost you, how much power do you use per month, where will you install the panels, what vendors are available to you, do you use more power in the winter or in the summer months, can the panel installation withstand the storms in your area, wind/hail/etc.)

Information about our prices and installation practices here in the US probably don't help you much if your available hardware, prices, and local laws are much different.

Do you have any solar/wind installations in your local neighborhood? If there are others, in our area, we can go down to the building department and probably find out what parts were used and who designed it--if we can't ask the owners directly. Also, if you are not the first person to do this in your town—it may be much easier for your installation.

Good Luck!

-Bill

So lets see if i got it right.

We generally get 10 - 11 hours of sunlight a day. lets say 3/4 of it is usable for solar applications therefore we get 7 - 8 hours of good sunlight.
if we use an average of 500W/h = 12000kWh a day we will need approx 2000W worth of solar panels right ?
now to store that kind of power i will need a 250Ah - 48V battery bank, double that for battery longevity = 500Ah - 48V battery bank.
i will also need an inverter/charger with automatic grid switching capabilities and capable of delivering 3,500W / 240V 50Hz peak at any point in time. I guess this would be a typical residential system.

What would the above parts cost in the US ?

I am planning to build this myself and if successful to offer the service to other people as noone in Malta offers such a service or the parts. i will therefore have to source the parts from overseas ( ideally at wholesale prices ) any idea where in Europe i can get these ?

Thanks again guys

First, you will need to calculate how much energy you will need... Because your system uses batteries instead of the utility to backup your power, you cannot take the excess energy generated during the summer and "bank" it for winter. You will only be able to bank a few days of energy with batteries.

So, if 500 watts per hour is your average maximum and it occurs during the winter you will have:

30 days x 24 hours x .5kW = 360 kWhrs per month.

360 kWhrs/month sounds like a reasonable amount of energy for here in the US assuming that you don't use a lot of electric heat or cooling. For example, I can get to a bit above 200 kWhrs per month with 2 adults, 2 young children, gas cooking/hot water, city water--basically just for lights, mostly laptop computer, refrigerator, freezer a couple small fans and cloths washer.

For the US, we have a map that gives us information on how much energy we can get from solar panels based on time of year and location.

US Solar Radiation Map Hopefully I can find one for Malta...

Looking around, found a short Malta university article on solar in Malta. There are a couple of names you can contact that may help you. The article says that flat roofs are common so you may need to build something to hold the panels at a ~36 degree angle (your latitude) or at +15 more degrees (~50 degrees) if you want to maximize your winter power (summer maximum would be at -15 degrees). You can also accept less power per panel and mount them flat if that works better for you. The US information allows you to account for the exact mounting arrangement.

Also, before proceeding too far, you may also want to look at solar hot water too... In my case, hot water probably accounts for a good portion of my gas costs (excluding winter heating). It may be a better match for you if your utility does not support "net metering"...

Here is a page with general European links (plus one to Malta).

Here looks like a good Solar Irradiation Map for Europe...

So, for:

Location: 35°51'48" North, 14°30'52" East, Elevation: 3 m a.s.l,

Nearest city: Valletta, Malta (0 km away)

Optimal inclination angle is: 32 degrees

Month
Irradiation at inclination: (Wh/m2/day) 40 deg.
Jan 4269
Feb 5205
Mar 5564
Apr 5786
May 5875
Jun 6048
Jul 6101
Aug 6597
Sep 6156
Oct 5475
Nov 4484
Dec 3866
Year 5452

There is a link that you can follow on this page that calculates the monthly estimated energy usage by your PV solar system. I believe, that you can use 0.95 (95% efficient) for a grid tied system or down to 0.75-0.80 for a battery interfaced system (or even less). I used 75% and 45 degrees facing south.

You can decide where your optimum point for spending money will be. At ~40 degrees, you will get almost 60% more power at summer peak than at the winter minimums...

Of course, this calculator does not account for exact cell types, or perhaps, even temperature... But it is a good start for you.

It looks like a 3kW peak system will generate just around ~300 kWhrs per Month for you during winter months. A one year average just over 360 kWhr and for the summer months, around 390 kWhrs.

Now for some links to various sources of hardware... Some will be manufacturer's sites which may not have prices, others, just a link to a solar site that has OK retail pricing. You may be able to save 25%-50% if you get a good wholesale price or can buy some used panels.

Here is one US manufacturer Xantrex. Happens to be the one I have installed (Grid Tie). A 3 kW peak GT inverter is something like $2,500 list (this will be your cheapest cost to install--anything else will be more because you will need charge controllers, inverters, some sort of grid interface, and of course batteries)... But you are looking for a battery based system--Xantrex has those too.

At this point, I am not even going to recommend something too you from this, or any other line... You will have to decide if you want to be 100% independent from the Grid, use the Grid as a manual backup, or something else.

Just for the sake of discussion, lets choose this unit. SW3048E a 3 kW, 48 VDC 230 VAC at 50 Hz unit with CE mark. Also has a generator input (perhaps, you can plug your utility power into this port for "backup". This place seems to be pretty cheap at $2,600 (list is around $3,500???). You will need a maximum of 88 amps at 44-66 VDC solar panels to power this unit. That is a minimum of ~3,900 watts of solar panels.

This same site also offers a bunch of solar panels... They seem to run, roughly $4.40 to $4.60 USD per Watt. Call it $4.50 per watt, and 3.9 kW will cost you about $18,000. Remember, even the best panels degrade at 0.7% per year and after 30 years will only be running at 80% of what they did new... So eventually you would need enough room for 25% more panels to keep the same amount of power (or ~$22,000 worth of panels at todays prices). By the way, while electronics are going down in price, PV panels and copper are going up in price because of the increased costs in energy and more people buying solar panels.

Next, batteries. Say you want 12 kWhrs per day of energy with 3 days of storage plus you only want to cycle down by 50% over those three days... And your inverter/power system is 80% efficient.

You would need 12kWhr x 3 x (1/50%) x 1/80%) =307.5 kWhrs of storage. Big fix needed here… It should have been =90 kWhrs of batteries… Fix everything below.

This is the equivalent in size of ~90 average, full size car batteries. Assume that this will give you an average life of 7 years with good batteries and nothing going wrong (you may easily get between 5 years and 10 or more years of useful life). Long life batteries should be in the area of 12-15 years.

Lets go to the same solar site and look at their batteries. Trojan batteries are a good mid-range quality maker. And lets look at there biggest 420 AH battery. 420 AH at 6 Volts = 2.52 kWhrs or 20 kWhrs per 8 battery string. 5 strings would give you 100 kWhrs of storage. That would be 40 batteries at $238 x 40 = $9,520 (list). If you only want 1 day storage, you probably can drop to 1/3 (2/5's is the closest here) of the number of batteries and only pay $3,808. You won't have the 3 day storage, and the batteries may not last quite as long because of deeper cycling, but 16 batteries are going to be much easier to maintain than 40 batteries.

We can also run the same calculation on a different brand of batteries that should have twice the life as the Trojans. Surrette, pick one of their larger batteries. Lets assume a 100 hour rate which is 9.25 kWhr capacity (8 volts). A string of six gives us = 55.5 kWhrs at $899 x 6 = $5,394. 2 strings would give us 111 kWhrs at $10,788.

It looks like the better batteries are worth it... They both cost about the same price in kWhrs (Trojan was 20 hr rate, Surrette was at 100 hr rate; at a 20 hour rate the Surrette price would be ~1/3 more or the 3 day Trojans 1/4 less--so this is not full apples to apples comparison) because of the longer life for the more expensive battery.

And, those Surrette batteries are heavy 193 kg (424 lbs) each, wet. Or 2.5 short tons of batteries.

At this point, your system would cost (list):

$2,600 3kW inverter/charger
$18-$22,000 for panels (20% loss for life, 20% loss for inverter)
$3,800-$9,500 for batteries. (20% loss for batteries/inverter)

Or somewhere in the neighborhood of $30,000 +/- for the major parts… Excluding copper wiring, fuses, bus bars, PV panel mounts, battery building, labor, permits, shipping costs and any local import duties.

END of fix for stupid math error…

Not accounted for. Wiring, mounts, losses due to shading (especially during winter), and labor.

As you can see, a huge part of the price is for panels and batteries… If you can reduce your power usage from 800 to 500, or even to less than 300 watts per hour, you can save a huge amount of money on the panels and batteries.

I really liked the idea of battery backup solar power for my area, but it just did not make any sense. If you can convince your utility (maybe with the help of your local university) to give you some type of Grid Tie option, your costs will be cut in half. Also, you will have almost zero maintenance for the next 30+ years…

I have to go now... But let me know if this is what you are looking for.

Sincerely,
Bill

PS Fixed a bad math error above and adjusted the costs below to account for the new values. -BB

Wow, great job guys, some of you should join us over at
http://www.wind-sun.com/smf/index.php
A great solar board I have been on for years.

The first thing I always say is reduce consumption, that is by far the cheapest way to go, then get solar for what you NEED to run. Replacing an old non-energy star electric fridge will save you more money then buying solar panels to power the old one.

reduce, reduce, reduce, then add solar.

The nice thing sizing a system for winter is you get a lot more in summer and can often run AC systems with the extra power

Thanks Bill, i guess that's all i needed to know and in great detail too.
thanks for the time taken.

it is quite costly ( more than i expected ) for an individual to help out the environment. I guess that defines " paying for your past mistakes "

Thanks again Bill

Another question:

What about building a solar Stirling engine.
It looks like a viable alternative considering that it is about 30% efficient and i do have a lathe so i can manufacture some parts myself ( i also sell air compressors so i already have some required parts ). i also already have a 'dynamo' from an old generator. i would therefore cut the cost of the solar panels which are the most expensive parts.

The only problem is that i do not fully understand exactly how the stirling engine works.

Does anyone here have any experience with this type of engine and is willing to give me a hand ?

Thanks again

A stirling engine works by having a hot side where gasses expand and a cold side where the condense again. It's just about the opposite of an air conditioner, where mechanical energy compresses the gasses.

Stirling engines are a great idea, but they have not become popular. I think it has to do with the relatively low power output for the size of the unit. I could be wrong.

Other sun -> power schemes include steam powered turbines and wind chimneys with a turbine. Other solar projects include passive heating and cooling.

Good luck with the project.

Daniel

Why a Stirling engine?

Unless you have a thermal source like an old volcano, you would still be stuck with building a reflector system to focus sun on the engine's hot zone to obtain high efficiencies. And, you will still be stuck with trying to figure out how to store the energy--same issues as with the solar PV.

If you wish, there are places on the web that sell small (desk top paper weight size) Sterling (and steam) Engines that you can experiment with. For example here is the US there is PM Research... I am sure that you can find others in Europe (if shipping/duties would be less).

I don't think a Sterling Engine is going to change any of the major issues for you... If costs PV costs are a big issue for you and you are handy, you may wish to try to go Solar PV but use a one or two axis solar tracking mount which could make the panels twice (and you can install 1/2 as many) as efficient for you. That would reduce the system cost by $9-$11,000.

I would believe that you would have to build a big parabolic reflector tracking mount with the Sterling Engine mounted at the focal point--probably would be a much bigger project.

Here is a press release on a very large Stirling Engine Solar project here in California...

I am always very happy to learn about new things in motive power--but I would be hard pressed to see this as near term project for a home do-it-yourself project.

If you are tying to go green and save money at the same time, following Brock's advise to reduce your usage and identify things that you can run with your solar system... For example, a deep freeze for food storage may be able to run only during daylight hours. You can run Air Conditioning during daylight hours (if you are home). Do you use a well pump? Do daylight pumping and a larger storage tank. Do you use space heating? Use solar hot water and hot water storage for heating and washing (solar heating using water or oil are very typical home built systems here in the US—and the price of fuel for water and spacing heating is also going up too).

What about fresh water? Malta has a desalination plant… So, if fresh water is expensive, using a solar powered desalinators plant would be interesting (if not expensive) option.

It looks like you have warm summers and cool winters, double pane windows with "Low E" glass and insulation (if you don't currently have any) may be a good project too. Also changing to CFL's and possibly new appliances are really you best place to start... A positive side effect for me was the reduction in noise (double pane vinyl framed windows and fiberglass insulation in walls, ceilings, and under floors) and a more comfortable home (no hot or cold spots near windows and doors).

Of course, if your home is limestone block, you have good thermal mass so wall (and floor?) insulation would probably not apply.

It still may be worth while to contact your utility (and local university) about bringing in a Grid Tie Inverter unit with a few panels for them to see and experiment with. If you can prove that they are safe and approved to US and European safety regulations (Xanterx offers a German variant of their Grid Tie 3 kW inverter), you may be able start the solar revolution there in Malta.

There is really no cheap technology out there (unless you want to include nuclear power) that I am aware of that allows us to be wasteful with energy and not have negative impacts on our environment...

-Bill

Amonra said:

it is quite costly ( more than i expected ) for an individual to help out the environment.

Click to expand...

Quite true! But not as costly as destroying the environment. It is all a matter of when and how you'd like to pay.

I'm thrilled that you're looking into this stuff. Soon you'll need an EV to suck up all that extra power.

Bill is right about the stirling engine biz. Neat idea, and there may be a place for it. But I'm not a fan of moving parts when static ones can get the job done - often for for less money, and almost always with less maintenance.

Why a stirling engine?

because it is more efficient and cheaper than a PV - from the article you mentioned "tests have shown the Stirling dish technology can produce electricity at significantly lower costs than other solar technologies"

"Stirling dish technology is almost twice as efficient as other solar technologies. These include parabolic troughs which use the sun's heat to create steam that drives turbines similar to those found in conventional power plants, and photovoltaic cells that rely on an expensive and increasingly limited raw material stock"

instead of a sun tracking parabola i was thinking of a dome constructed out of many fresnel lenses which would concentrate the heat on to the engine.

building the engine itself would take a lot of time but i dont think it would cost too much as it is made out of common materials like aluminum.

i dont know about the solar revolution simply because of economics -
$30,000 = 4 years average person's wage in Malta so i dont think many people will be willing to spend that much on a PV solar panel system.

There is only one electricity supplier on the island which is government owned and will not let go of the monopoly they currently enjoy. the power plant is generating a revenue for the government therefore asking the government to buy electricity from an individual rather than selling it would be like asking the government to pay taxes to the people rather than the ppl paying taxes to the government. therefore a grid-tie system is not an option, at least not yet.

I have not seen many (if any) home made Stirling Engines that can produce a lot of power from solar... If there are, that would be great to hear about!

Regarding the "dome constructed out of many Frasnel lenses", please correct me if I am wrong--but I am imagining a 1/2 "round" structure covered with, say 1 meter square Fresnel lenses, each pointing towards the center where the engine's "boiler" would be located.. In reality, I would guess that this would be a band, or several, of fixed lenses pointing at the center point.

If I understand your design correctly, then each lens will point at one segment of the sun's track.

I don't believe that this would work because each lens, at most, can gather and focus 1 sq meter worth of energy at the engine at a time. All the other lenses will be projecting an "off square" image at some other place than the engine's boiler.

The reason for the mirrors is because they not only focus the light they also redirect it towards a fixed focal point. And, they will maintain this fixed focal point because the whole unit tracks the sun's arc across the sky.

So instead of having ~1 sq meter of sun's energy focused via one lens, you would have several hundred sq meters of sun's energy from all of the parabolic reflectors jointly pointing at the boiler...

The only way that I can imagine using a Fresnel lens would work is if it was one big lens 10 x 10 meters (or whatever size/shape needed) that is constantly aimed at the sun via two axis tracking.

-Bill

i have been trying to find detailed plans to build a stirling engine but could not find. Would anyone have these pland by any chance ?

Amonra

I don't have any plans... at that PM Research link above, there are about 8 books from $10.50 to $40.00 (USD)...

Here is a Japan based web site (English version) with several simple engines (and, it looks like) enough plans to build a simple engine or three...

A Google search brings up lots of links for engines and plans...

Please let us know if you find/build something interesting!

-Bill

Your best bet is to check out Home Power magazine... everything from conservation to solar to wind power to hydro power... even some biodiesel.

http://www.homepower.com