Solar vs wind power

Factual Questions
1

This is NOT a homework problem. But I’m currently doing a cost/benefit study that hopefully will help make a decison between installing a solar or a wind power system on a rather isolated island in the Washington San Juans.

One of the things this will require is finding out average wind speeds over the area, and also finding out how much average power in watts is contained in sunlight falling on the ground here. The first was easy - quickly found an average wind speed chart, by months, for areas near here.

The second is giving my Google-fu a little trouble. I know such data exists, but haven’t been able to lay my hands on it. If any of you Dopers knows of a web site containing this information I would much appreciate it.

Thanks a bunch.

2

You can see data for a few cities in Washington here, with a couple of different tracking options. It’s not the San Juans, but it’s at least in the area.

If you have DEMs and access to ArcGIS, I think ESRI has a routine that can calculate solar radiation based on the elevation, aspect, latitude, and time of year - PM me if you want more information about that.

3

You’ve got to compare consistency of either solar or wind availability, too, or have a helluva huge battery bank. If it clouds up and rains for four days straight, you will be essentially with no power, unless you have a generator for backup.

Some wind generators stop working if the wind velocity exceeds a certain speed. So you could have gale-force winds, but no juice going to the batteries.

And wind turbines can be GREAT attractors for lightning strikes–one of those, and unless you’ve got a bunch of safety circuit breakers built into the system, all of your electrical stuff will be fried.

Also consider that major appliances may need to be replaced with “Energy Star” appliances.
~VOW

4

Don’t you have a weather service in the US that tracks the conditions for each day for most areas? If it is a very isolated (small) island and therefore doesn’t have it’s own weather reporting station, the next land-based spot should have.

However, local conditions, esp. on a small island surrounded by much water, can vary much - more clouds/ mist or more wind=> sun.

Over here, we start with the DWD observations on sunshine, but for wind, most companies prefer their own measurements for big plants, because wind at ground level (up to 2 m) (measured for weather service) is different than wind at 50 yards height or at 200 yards.

The lower the height where you wind wheel is , the more the wind speed and amount will be affected by local terrain conditions - valleys vs. ridges, and eddies and swirls.

The other question is what you need the power for - if you have a small home and need heat as well as power, solar thermic makes sense indepent of PV for power. (Or if there are enough trees, a modern oven - pellet oven, high-temp. oven).

And there’s also the question of power usage - mostly during the day or during the night? Continuously or can you shift the usage to available times?

Generally, over the broad population, most power is used during the day, for AC to shops and offices, but individual use (esp. on a small island) can vary widely.

Combining wind and solar could also cut down on battery usage if for example sun shines during the day, and the wind strongly during morning and evening (land wind, sea wind close to the shore) for supplement, and you schedule your activities so you don’t need power at night).

5

As an aside, is this going to be the exclusive power source for the area, or is this more of a means of mitigating the costs of conventional power? I’ve heard of folks setting up their own windmills or solar cells, with the result being that they drew less (as opposed to no) power from the grid.

I’m more curious than anything, I’m not sure if it’d be relevant aside from addressing concerns about low production periods for one or the other.

6

Generally, it’s best to have a mix of Wind and Solar. Typically, it’s cloudy and windy, and clear and sunny, so the two compliment each other.

7

Make sure you’re using the winds aloft and not surface winds. They’re quite different.

8

You can get a lot of information from RETScreen. It is provided free-of-charge by the Government of Canada from here.

9

Thanks to all for your replies - that web site giving solar radiation in the Washington area looks close to what I’m after.

Since there is appears to be some interest in this subject, here are some of the details of the situation.

The island is almost exclusively used for recreational purposes, and is totally isolated from shore facilities; so we have to provide all of the utilities that are used. The installation will be to supplement the electrical system for our caretakers. And yes, they have a large battery bank, connected to an electrical inverter to change the 12 V battery voltage to 120 V house voltage. This bank is charged by generators, either a 50 KW genset that runs whenever the reverse osmosis water machines are making water, or a 4 KW set that is turned on whenever the batteries may be getting low.

We have tried a small windmill (400W), but primarily because we went on the cheap and got a low priced one, this has not been satisfactory because of continual maintenance issues. The generator system works pretty well, particularly as the island is making a lot of water in the summer when the island has quite a few more occupants than in the winter and thus the batteries are getting charged a lot with spare electricity from the big generator.

However, in the winter we have to run the smaller genset on a daily basis, and this is what we are trying to cut down on.

Of course, in the winter here in the great Pacific Northwet, we sometimes are a little short on sunshine. So we’re trying to balance out the solar vs wind generation.

For those of you who are further interested, the web site of the island can be found at;

http://elizaislandbeachclub.org

10

Make sure that during the off-season, someone checks on the batteries. They are an enormous investment in any “do-it-yourself” electricity venture, and the water levels have to be maintained.
~VOW

11

The caretakers are in residence for the entire year, so are available for maintenance whenever needed.

12

If the island is used for recreation, your wind wheels are probably strongly limited in size because the big wheels used for commercials plants today would be a bit of an eyesore on a small island.

There are two alternatives to normal windwheels that might be interesting, though I don’t know about maintenance:

a company called timber tower is building the trunks out of wooden boards planked with plastic foil (to reduce drag), which is more enviromentally friendly and easier to build - esp. on a remote island - than the usual tower of concrete and steel.

a small alternative guy is installing tiny wind wheels in tree tops to get around the limit that (in Germany) requires a permit for normal-sized wheels. He claims by linking together several wheels he can power one house, or a network can power several houses.

Do you have wild storms instead in the winter, or lots of fog? Because with stormy weather, wind would be “ideal” for winter, and solar for summer.

Note: wind wheels do require a lot of maintenance because they are moving parts and need a good shut-off system before a storm, otherwise the wheel can get damaged.

Does the island have tides or currents? There are now small underwater turbines being tested on the seabed near a shore or in the opening of a river to use smaller currents/ tides than big plants. The tests are about effects on the fishes -they don’t want the shred the fishes. So far it looks as if the fishes swim around it and aren’t being sucked into it.

You could also look into the European project at the university of the Agean (in Greece) where they built a floating wind wheel/ solar platform to desalinate sea water to supply a nearby small island (and the salt produced attracted algae, which attracted clams, which attracted fish, which the men who inspect the platform catch.) The project started several years ago and was supposed to run for 20 years as test; the inhabitants were delighted at the quality and amount of drinking water, but I haven’t heard anything since.

13

These sound like they are only in the experimental phase now, and we definitly don’t want to be out there on the cutting edge of technology. Maybe after twenty five or so years, but not now.

I would think that water turbines are also mostly experimental, and while we do have good tidal flow, I can see monumental maintenance problems. And the permiting process that would be necessary before installation would also be monumental.

So it looks like the only options we would consider are solar panels, and regular wind turbines.

14

This may sounds weird but if you’re on an island why not use a micro hydro system tied into the coastal currents?

15

Why do you think water turbines would need more maintenance than wind? Esp. if the currents/ tides are more regular than wind usually.

Any system that has moving parts or connects to some electric machine, will require maintenance, whether it’s a diesel generator, a wind wheel or what Grey calls Micro hydro power.

In the second Jurassic Park novel, where they go the deserted island where the dinosaurs lived in the wild, although the whole place was abandoned several years ago, they find that there is still electricity (and wireless network) there - because it’s a volcanic island, the scientists installed a geothermic plant with gold-plated turbine to minimize oxidation. (The turbine is caked with sulfur, though).

So you might ask universities who have labs in out-of-the-way places like Antartica or remote mountain tops what they use there, or university institutes who are doing research in renewable energies on what’s the most rugged version of a power plant.

The more rugged the plant is to require less maintenance usually means it costs more, though.

16

Actually, guys, we’re trying to do a cost comparison between two relatively mature systems, solar and wind power, and trying to come up with the most efficient system at a moderate cost. Things like tidal generators, etc., are way beyond the scope of our intentions.

17

Well a sad bit of truth is that I doubt any online source can provide you with exacting and specific data about average wind speeds at a specific elevation on your island (which looks beautiful by the by). To acquire that information you’d need a tower holding an anemometer at a given height, or better yet several at different heights. Then you’d need to keep that in place for a long period of time and continue recording the results. The longer your sample period, the greater value your predictive data would be. In short, you’ll likely never have enough data to completely compare the energy potential of wind vs. solar on your property without investing in both and finding out for yourself.

A few years ago I was involved in a rather long term internet argument with a man who ran a company named “Freetricity” which sold small scale wind turbines. The claims he made about his products were preposterous to the degree I was rather sure he was committing fraud. I wouldn’t have given his companies name in a context like this but last I saw he was facing more than 90 charges of grand theft and of selling illegal marketing schemes (he had an affiliate program). So while I claim absolutely no expertise in legitimate alternative energy systems I do know a thing or two about the sales pitches of the more fraudulent ones.

First off, when it comes to wind power there really is no substitute for height. As air flows over ground contours, buildings, trees or what not it not only slows down but it becomes turbulent, either of those rob you of the energy you need to spin your turbine. The problem being that in order to get your turbine up high enough to operate efficiently you’ll end up spending near as much for a tower as you will for the turbine. This also means that if the zerk fittings you need to keep filled with grease so your bearings don’t wear out are 50 feet off the ground the grease gun you’ll use to do that needs to be 50 feet off the ground, and you with it.

Perhaps you begin to perceive why some “less than honorable” turbine manufacturers try to pretend that they have “revolutionary” new units that either don’t need tall mounts or even worse still, can be mounted on your home. That link is from Paul Gipe’s Wind-Works dot org, he doesn’t sell turbines, he writes books about them. He’s a passionate promoter of wind power and I found him to be an excellent resource in debunking the claims of the less than ethical turbine merchants, and general information on the topic as well.

I agree with the people who say go with both wind and solar. Both have advantages and disadvantages (solar can be mounted on your roof, all but toy turbines can’t). It’s easier to price compare solar cells than rival turbine designs, I do not in any way wish to discourage you from investing in wind power I just want to make sure the salesman’s advice is the only advice you seek before handing over your money. Green energy is not immune to scam artists.

18

To add to Ennui: we don’t have enough data for your specific problem to give you a good enough cost/benefit analysis.

You asked for weather data specificially, and ennui elaborated even more why winds measured by the weather service at about 2m are not helpful when considering a wind tower at 30 or 50m above ground.

You have to factor in a lot of costs: maintenance (like I said, wind wheels have lots of rotating parts and varying stress, so they need a lot of maintenance). In addition, there’s the cost of transporting and setting up the tower, which in a remote island can be quite high (you don’t want huge bulldozers tearing through your resort?)

I’m also not quite clear why it has to be one or the other - why not solar for summer, and wind for winter?

What I would recommend is to contact your local proper enviromental group (Greenpeace or others - I don’t know what else you have in your country, I think Sierra Club?) or true citizens advocacy group in your area and ask them. Often they have solar clubs that help people doing the estimates or at least a list of respectable companies that would do the whole set-up.

But be prepared for wind to invest in preliminary measuring. This is one of the things that make wind more expensive than solar (Where the sunshine length is already recorded by weather service) and why wind is usually done in large parks (in addition with being eyesore).

The local enviroment group could also advise you about bird migration patterns, so you don’t disrupt them, and a good company should also select a quiet wheel (Depending on size, terrain and distance, some wheels can emit an annoying hum at a special frequency - at least some people claim to hear it, while others say those claims are bogus. By choosing the right size and testing it, you can eliminate that before everything is finished).

19

Solar panels still generate some power when it is clouldy. Also solar planels require less maintenance because they don’t have any moving parts, but you do need to make sure the panels stay clean to ensure maximum efficiency.

20

Depends on the location: downwind from trees with leaves and pollen? Close to water with salt spray?

Solar plants plan for yearly cleaning for maximum efficiency, usually twice per year, but in dirty locations (on the roof of a farm shed) up to 5 times a year.

Since this isn’t in the city, you don’t have to put the panels onto the roof, but can put them on the ground, making cleaning much easier.