Bottom’s Up!

Here in Aruba, windmills will soon be turning. A friend and I headed to the south east side of the island where the foundations are now going in for some very large turbines that will soon capture the energy of the trade winds and turn it into electricity for the island. Here’s a look at how the foundations are built.

First, a site is excavated and a pad of concrete is poured with large rebar to tie it together with the next level of the foundation.

windbasbThen a cage of rebar is set up like this:

webascWith the man standing on the left in the photo above, you get a sense of the scale of this structure. Finally, the concrete is poured around the rebar to complete the base, which looks like this:

windbasdSoon there will be towers standing atop these bases. Then will come the turbines themselves with their massive blades turning in the wind.

I can’t wait to see this project delivering power to the grid in Aruba. It will be a giant leap forward for the island.

Published in: on August 11, 2009 at 6:43 pm  Leave a Comment  
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Island Power, Inverters

The DC/AC inverter is the heart of any off-grid power system with electricity produced by solar and wind. Most small wind turbines and solar panels produce direct current (DC) electricity. However, the electricity you use in your home is alternating current (AC). We won’t bog down here with the details of that. Suffice it to say that you need to convert the DC to AC. The device that does this is called an inverter. The inverter draws power from the wind turbine and solar panels as well as from the batteries in the system. It then delivers it to the system in clean, regulated, AC form. Here’s a look a stack of four inverters as part of a system built by Outback Power.

Those four magic block boxes, one on top of each other, are the inverters. Each one of those takes 48 volt DC current and converts it to 120 volt AC current. The output of each one is combined in the adjacent boxes so that you can have both 120 and 240 volts. This system, with its four inverters produces a maximum of 10,000 watts of steady power. It can handle a surge load for a brief period of up to 14,000 watts.

10,000 watts is enough to power my entire house in Aruba, including those two power-hungry air conditioners. I rarely run them at the same time. Nonetheless, I’ve over-sized the system to handle the demand. Over-sizing is the key to happiness with off-grid systems (and pick-up trucks). It is always cheaper to build a larger system at the beginning than to upgrade later.

Lately, these systems have been growing in popularity. Companies like Outback have made them easier to set up, more efficient, and less maintenance intensive. Similarly, contractors have used them in “plug and play” systems that are easy for homeowners to understand. I can’t wait to have mine working and putting the money back into my own pocket instead of paying a utility company.

Published in: on August 31, 2008 at 10:45 am  Leave a Comment  
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Island Energy Production

So in the last post, I said I needed to DELIVER 7,000 watts of power to keep my airco system working here in Aruba. The next logical question is how am I going to produce electricity in the first place. Well, here in Aruba we have copious supplies of both wind and sun. The trade winds blow across this island day and night, month after month, we few exceptions. My own observations show that the average wind speed on my property is in excess of 24 mph. As for the sun, it blazes at least 8 hours a day. Cloudy and rainy days do occur but not very often and rarely several in a row.

So, how do we get the wind to make electricity? With one of these:

To the left is a Southwest Wind Power, Whisper 200, wind turbine. More commonly referred to as a “windmill.” The unit produces a maximum of 1,000 watts of power when a steady breeze of 27 mph is passing through its blades. But wait a minute, I said my average speed is only 24 mph. That’s right and at 24 mph this unit produces 800 watts. To keep it simple, this wind turbine could (theoretically) power an electrical device requiring 800 watts of power given  the conditions I described.

In the real world, things are a bit different. Here’s where we all have to concentrate. Let’s say that at my house the wind blows at 24mph for 10 hours each day. That means the windmill would produce 800 watts times 10 hours for a total of 8,000 watts. What can 8,000 watts do? It could run that big airco of mine for a little more than 2 hours. Now, my on-site observations show that the wind blows MORE than 24 mph for approximately 20 hours per day (yes, it is that windy in Aruba). So, I can reasonably expect this unit to deliver 16,000 watts per day to the system.

I did mention something about the sun. The example is much the same with different equipment. A solar panel like the one on the left does the job. Yeah, it’s one of those sort of shiny blue things that typically goes on the roof. My system will use 200 watt panels. Each one will produce 200 watts if operating at its maximum. I’m going to string 5 of them together to have the potential for 1,000 watts. Again, I’m going to de-rate the output to 800 watts and I’m going to say that it will produce that much 7 hours per day for a total of 5,600 watts per day.

Now it is time to combine these two sources. Together, I’m expecting them to produce a total of 21,500 watts per day. Let’s round DOWN again, to 21,000. Finally we get to the fun part. What can I do with the 21,000 watts and those airco units? Just divide the production by the demand. I could run them both for 3 hours since they require 7,000 watts together. I could run the larger one for about 6.5 hours, or the smaller one 7 hours, or some combination of both. Since I rounded demand UP and production DOWN, I should have some room to maneuver here.

Either way, I’m satisfied that this method of production will give me what I want, which is to run those air conditioners long enough to keep my cat, my wife, and myself comfortable here in Aruba. Next time I’ll talk about combining this power into a manageable form. In between, we’ll have some more fun on the island, writing books, and taking photos.

Island Energy (Demand) Calculations

We’ve been having fun, traipsing around Aruba, looking at beaches, checking out the sights, dining at all kinds of restaurants. However, having a house here is like having a house most anywhere else in the sense that utilities are a serious issue. The cost of electricity in Aruba is quite high because they burn oil to make it. (I’m not going to get into the politics of this just now. Suffice it to say that I believe in private solutions.)

My original goal for the house was to power the air conditioning system off the grid. Thus, the question, “How much power do I need to produce to get those airco’s off the grid?” The answer follows:

Last year, I installed two brand new split-type air-conditioners. The larger one uses 14.4 amps of power at 220 volts which means approximately 3168 watts. The smaller one uses 12.6 amps at 220 volts, consuming 2772 watts. Add those two together and you end up with at least 5,940 watts. When it comes to power use, I like to round UP. Therefore, at a minimum, I need to produce 6,000 watts of electricity to run both air conditioners at the same time. But wait a minute! When you first turn the airco on, it draws a bit more power to get started. So, let’s set the minimum at 7,000 watts. To correct myself slightly, I need to DELIVER that many watts to keep these unit cranking.

Okay, how am I going to do this? Production will come from a wind turbine and solar panels (photovoltaic). This power will have to be converted from direct current (DC) to alternating current (AC). How is that going to be done? With an INVERTER. What if the wind isn’t blowing and the sun isn’t shining? Electricity will be stored in a BATTERY BANK. How is the battery bank going to be charged? Through the inverter and a CHARGE CONTROLLER.

Are you still with me? I hope so. None of this is as complicated as it sounds and there are some details that aren’t discussed here. (Please, if i made any mistakes, let me know so I can correct them.) You can purchase entire systems that are basically “plug and play.” A qualified electrician can have you up and running in no time.

Now, the next post is going to look at ENERGY PRODUCTION for this system. There will be pictures, too. Remember one thing: Once the system is operating, you get a return on your investment and protection against future price increases. Every time the price of energy goes up, it’s as if you’re saving more. And you are because you have a fixed cost for your system and a little extra for the maintenance.

Enough for now. Stay tuned. And don’t forget that you can control your energy consumption AND production. Don’t let anyone tell you differently. You have to be willing to change a little or a lot depending on your goals. However, you do not have to live in a cave, eating berries.