EnviroMission Limited (www.enviromission.com.au) produced this 5 minute video on the pilot plant in Spain. It is an older video (2000) but gives a decent understanding of the solar tower concept. EnviroMission, Ltd. (US Market: EVOMY, Australian Exchange: EVM) is a renewable energy developer of sustainable “green” energy solutions for the energy market. EnviroMission aims to be one of Australia’s leading producers of clean renewable energy. EnviroMission holds the proprietary rights to Solar Tower technology, a large-scale renewable energy technology based on simple fundamentals of physics — hot air rises. Solar Tower technology has the potential to offer competitive renewable energy with equal reliability to fossil fuel generators. A single 200MW Solar Tower power station will provide enough electricity to power around 400000 households. The energy output will represent an annual saving of more than 1960000 tonnes of greenhouse CO2 gases from entering the environment when compared to brown coal emissions in Victoria. The greenhouse savings equate to the removal of approximately 500000 cars from the road. The Australian Solar Tower project consists of six distinct phases, the first two of which (project optimization and pre-feasibility commercialization) have already been completed. The third phase (final feasibility), paving the way for the implementation of the next three phases (final design, construction, and commercial operation).

See the original post: Solar Tower – renewable energy green global warming

First you will need a base to place the solar cells on in order to make a panel. You need enough solar cells (about 80) to layout a fairly large surface area. You will notice that there are two distinct sides to a solar cell.

The front looks kind of a blue color while the back looks very much like the back of a mirror. It is essential that you set up the cells with the blue or upper surface facing toward the sun.

putting solar cells together

Each solar cell will create not much more than one half a volt DC usually. The voltage remains the same. As the size of the cells increase, depending on what you get, the current or amperage will increase.

You can place the solar cells out on the floor before you begin, like a deck of cards. Leave a space between each cell of about one quarter inch. Arrange the cells in rows until you have a shape that is pleasing to you. You want to make the finished panels slightly narrower in the width so they are easier to handle, but you can do as you like.

Once you have the cells laid out in the pattern you want, measure the outside dimensions of the rows. You need to know how big to make the backing board. You will attach the solar panels to this board so you need to know how big it is.

backing board of solar cells

With 80 cells you should end up with a panel that produces approximately 100 watts of power.

You can use some plywood or any kind of strong lumber. The nice thing about the plywood is that you don’t have to join it together. After getting the outside measurements we assess what glass we will have to cover the upper portion of the panel. You can put 2 inch spacers on top with a ventilation space around the panels as well.

The glass will usually need a support in the middle too so leave room for that as well.

Let’s say that the layout of the cells added up to a size of 24 inches wide and 40 inches high including the spaces between the cells. If we wanted a 2 inch spacer in the middle and all the way around the outside to support the glass then our plywood should be cut to 30 inches by 46 inches. In this way we could fit the cells on the plywood and still have support for the glass.

Before you begin to put the cells down on the plywood we first treat the plywood with an epoxy sealer that is designed for UV protection. It sinks right into the wood and protects it long term from the weather.

The holes in the dividers will have the wires from the cells meeting and joining to form the circuitry of the panel. The holes also allow a certain amount of ventilation too. Make sure you put at least 3 coats of the epoxy on everything as it will be exposed to some rough weather at times.

Get any kind of soldering gun with at least 25 watt and use silver bearing solder for soldering purposes, which you will need in the next step.

In our next post: connecting the cells together…

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Start by quartering a 48 inch long piece of pipe around its circumference and cutting it lengthwise into four pieces. You can check the post on How To Cut The Blades for this.

This will end up being a wind generator blade assembly of just over 8 feet in diameter. Adjust your lengths according to your own preferences.

Remember that you will need a blade diameter of approximately 8 feet to achieve an output of 1000 watts with a 20 mile per hour wind speed. A couple things you should remember though. The most important is the tremendous force the wind can place on your equipment if your blades are too big. Let’s assume a wind speed of 55 miles per hour, that’s really a common speed out there. If your wind generator blade assembly has a diameter of 3 feet the force on the blades is approximately 115 pounds. But, if you up that blade diameter to the 8 feet (we recommend for most projects) the force of the wind on your wind generator at a wind speed of 55 miles per hour is an incredible 840 pounds of force.

Now, your blades are not catching all of that force of course, but they are catching a great deal of it. We design our wind generators to handle these forces. Design your tower, blade and hub assembly with that in mind. Light is good for spinning, but strong is better. It is sometimes hard to strike the right balance, but new materials and sometimes some surprisingly old materials make the choices easier.

Attaching the blades to the hub

The pulley that makes up the central part of your hub assembly must fit tightly on the shaft of the DC motor. The hub assembly must spin the DC motor in order to produce power.

We usually drill a hole through the pulley and shaft and insert a small one eight of an inch bolt and nut to hold the two together.

On the pulley (hub) you will have to measure the circumference, or distance around the outside of the pulley. For a three blade assembly you will divide this number by 3 to give you the distance between the blade mounting pieces of steel.

The following diagram shows the placement of the steel on the hub for use with PVC blades.

Note: when using wooden blades make sure to use 1 inch angle iron so that the blades are mounted at an angle to the wind. We have found 1 inch by 2 inch works about the best. The blades should be mounted at an angle of about 10 degrees to the wind.

The steel should be drilled with a one quarter inch drill bit at the same position on the hub for each piece. This will vary depending on the hub material used. The above diagram gives you a good idea of how to do it. Keep the holes at least one inch in from the outside if possible for strength and they should just meet at the centre of the hub. Take your time during this process and you will have a wind generator that is well balanced and spins well. You will be glad you did.

Mounting the Blade Assembly on the DC motor

First we need to do a bit of testing to see if your blade assembly is balanced. Just place the whole thing on a shaft of similar size and give it a few spins.

Make a note of the place it stops each time. If you notice that the same blade is always facing down at the end of each spin, then it is a wee bit heavier. Just give it a quick trim until none of the blades consistently stops at the bottom.

You can now do a test mount of the blade assembly on the shaft of the DC motor.

In our next post we will cover how to build a mount for the DC motor. Stay tuned