DIY Wind Turbine - Part 2 - Components

And so, the search was on to find some components to build the wind turbine and services to store the electricity generated by the turbine and convert it to 240V AC, a more house hold appliance friendly voltage. Although there are a lot of online sites dedicated to wind turbines, most of the parts required to build the full system are very expensive, so i started looking for alternatives, i had already decided that i was going to build the turbine myself, but what about the battery charge regulator and 12V DC to 240V AC inverter? These are parts i need to buy, if i am to get the system up and running quickly.

GENERATOR:

As described in 'Part 1' of this blog the genorator that i am going to use will be a DC Permanent Magnet motor, salvaged from some other device, it has to be high voltage at low rpm, so i set about trauling t'internet for such a motor...

Hours later i had stumbled across a site that sells new and used exercise machines, and parts. One of their parts interested me the most, it was a 4000RPM @ 180V DC PM motor, for use in running machines, it even had a pre balanced fly wheel that i could use to attach my turbine blades. A quick linear calculation (with 100% efficiency) gives 12V @ 266RPM (the minimum voltage required to charge the battery). I am not sure what wind speed will be required to turn the turbine at 266RPM but i am hoping the ambient wind speed where i live will do the trick, i also don't know what that wind speed is at the moment, this will also depend of cousre on my blades.

I ordered the motor and it was delivered the next day, surprisingly heavy at 7KG but did have the mounting bracket still attached, a quick measurement of the output voltage gave 5-7V DC simply twisting the rotor between my fingers, seems like it may do the trick.

BLADES:

I had read some interesting blogs describing fabrication of the turbine blades from sections of plastic pipe. Although these blade would be very crude and not as efficient as commercially available blades, the cost to make them would be next to nothing, especially since as i have some guttering lying about in the garden. The guttering is not very thick and i am wondering if blades made from this material will stand up to a strong gust. So i will make two sets of blades, one from the scrap guttering and one from waste pipe, which is substantially thicker. All of these parts can be found in your local DI|Y store.

BATTERY:

Lead acid batteries are typically not very good for this application unless the discharge of the battery is closely regulated, they are easily damaged by regular deep discharging, and as i wanted to use a 12V car battery using one is not ideal, the plus side is a small battery will only set you back about £60. I went to my local battery store to find that they also sold lesuire batteries, a bit more expensive than a car battery but with higher capacity, and the added benefit of being able to withstand deep discharging. I opted for the larger 110AH battery as it would store more charge and mean i would require a smaller number of batteries to supply the power i need. If the turbine produces surplus i can always purchase another later on.

I performed a quick calculation on my iPod Touch to see how long my laptop would last if running soley from the battery (no turbine), the power required for my laptop as stated by the power supply is 65W (not bad for a dual core machine, but then its and AMD processor :)), the inverter will use 12V so the current required is: 65/12 = 5.4A, so if the battery can supply 110A for an hour the laptop sould last approximately 110/5.4 = 20 Hours

The alternative way of calculating this would be to convert the battery to Watts 110*12 = 1320W (for 1 hour), so 1320/65 = 20 Hours.

My mind was made up, i bought the battery and a set of double ended (for battery expansion) battery terminals for £160.

INVERTER:

The inverter will probably be one of the most expensive parts in your system, however, i found a very nice inverter for use in caravans and cars at my local camping centre. They had a wide range, from 100W to 1000W, all of which are ideal for this application, but if i am to connect more than one device at a time to the system i would require a larger unit, so i opted for the 1000W version, it connects directly to your battery, and it also has low voltage warning when the battery drops to 10.V and shutoff at 10V, so although i have a deep discharge capable battery it will never drop below 10V. I had to order the inverter, but at £130 i dint mind, waiting.

CHARGE CONTROLLER:

While i was looking through the catalog at the camping centre for inverters i noticed that they also sold a range of 12V battery charge controllers. These units prevent your battery being over charged by your turbine or solar cells, and give you an indication as to the charge rate and current battery status. Some controllers can shitch the power generated by your system to another load or battery once the first battery is fully charged, but the unit i purchased just disconnects the battery. If the turbine ever does produce surplus i will just add another battery and connect it in parallel to the existing battery, so any disconnecting of the battery will occur less frequently, minimising wasted power. The charge controller was £100 and was ordered with the inverters.

VOLTAGE DOUBLER:

To boost the charging performance of the turbine in low wind speeds i have also ordered some 6-12V voltage doublers, the input voltage range of this unit is 4-11V, they have not been delivered yet and i may not even need them but i go them just in case. I could also use them to boost output of smaller motors.

MISC:

With some of the parts on order i have some time to concentrate on fabricating the blades and building the turbine mountings and tail. These will utilise the bracket that came fixed to the motor and some other bits of scrap. i may need to get a tail made as i have yet been unable to find a suitable piece of metal or plastic to use. Thats it for now, but part 3 will describe fabrication of the blades, once i have worked out how to do it...