Wednesday, August 5, 2015

The solar bore pump - part 1

Windmills were once ubiquitous in the rural landscape, but you might have noticed something new appearing in their place. Increasingly farmers are choosing to replace old windmills and equip new bores and dams with solar panels instead. Like windmills, solar panels use renewable energy and have very low running costs. Solar panels and pumps, however, are now cheaper to set up and to maintain, giving them the advantage over windmills for remote applications. Even where access to grid electricity is available, with increasing electricity prices, the use of a free energy source is desirable. And they are far more practical than diesel or petrol pumps which must be attended regularly for starting, stopping, maintaining and refuelling. 


eight acres: our solar bore pump project
 

The disadvantage of a solar pump, like a windmill, is that the power source is not always available on demand. A windmill will only pump water while the wind is blowing, and similarly, solar panels will only power a pump while the sun is shining. This intermittent supply can be managed using tanks and troughs to store water while the energy source is available. Tanks are often placed at high-points on the property, so that gravity can be used to distribute water as required. Alternatively, the panels could be set up with battery storage so that the pump can operate continuously.  

Our bore is in a low area of our property, but the bore is relatively shallow. We chose a pump that could pump the water out of the bore and up to the highest point on our property.  We've installed a tank there and will gravity feed water to where its needed.

Setting up a solar pump may sound complex, but actually it is very simple and with a few instructions, anyone can make use of renewable energy to pump water on the farm. Most suppliers of solar panels and pumps will provide assistance to size the pump and basic instructions for installation.

Whether you need to pump water to provide water for stock, or to irrigate paddocks, you need to choose the right pump for the amount of water and the distance and height you need to move the water. No matter what type of pump, whether its powered by solar, fuel or electricity, you will need to know three things in order to select the correct pump. The first is the volume of water you need to move, second the total “pressure head”, which is a combination of the height and any resistance of the pipework, and finally, the “suction head”, which is the distance from the pump to the water level. A pump supplier can assist with selecting a suitable pump when provided with these three factors.

The first step is to work out the volume you need to pump. For cattle you can assume they will drink 100 L per day. For example, to provide water for two cows, the pump would need to be capable of moving 200 L per day. Note that the pump will only be available while the sun is shining on the solar panels, which in winter may be only 6 hours per day, in which case the pump would need to achieve a flowrate of 200 L in 6 hours, or 33 L per hour.

The total head that the pump needs to move the water will depend on both the height and the pipework to be used. The height can be determined roughly using GPS devices or from contour maps, to the nearest 10 m if possible. Unless it’s very complicated, the pipework typically has only a minor contribution to the total head. Again, a pump supplier can assist with these calculations.

Installation of the pump and solar panels will require a suitable location with maximum possible sun exposure and a northerly aspect (in the Southern Hemisphere). The ideal angle for the panels depends on the season, but on average, the latitude of the location is a good angle to use (unless the angle is to be adjusted with the seasons and in that case, the ideal angle can be worked out from the sun angle at each season). A sturdy frame should be constructed to support the panels if this is not provided as part of the package. Also consider fencing the panels and pumps to prevent damage from curious cattle, they tend to use anything as a scratching post.

A solar pump is a good alternative to windmills, electric and fuel pumps because it is cheaper to operate and requires minimal maintenance once installed. A pump supplier can assist with calculations to determine the size of pump and panels required for a any application. While they may seem complicated, it is worth investigating if a solar pump is suitable as they are now relatively simple to install and operate.

Have you considered using a solar pump?  Or other solar devices on your property?  I'm thinking about writing a more detailed eBook about the steps required to set up the bore pump and the solar panels as it was difficult for us to find that information - would you find this useful?


4 comments:

  1. We looked into a solar pump. The response we got from suppliers was 'why would you want to do that?'. The prices they quoted were ridiculous for our situation. The cheapest was $6000. We put in an electric pump that does the job well and will install solar panels on the house to supply power. We are lucky that where we need the pump is relatively close to the house so we dug a trench and got a powerpoint installed close to the pump. This won't work if your pump needs to be in the middle of nowhere.

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    Replies
    1. Wow that is expensive, I understand why you would use an electric pump in that situation. Our whole system was more like $2000 (plus our time to set it all up), and considering we have no power at that site, our only other option was a windmill. Unfortunately most businesses are offering expensive solutions to simple problems and that is preventing people from using solar pumps.

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  2. I bought a Sunpumps Solar Pump SDS-D-128 and a Solar Slowpump 1304-12 VDC Surface Pump for my small farm, but I have never had the chance to install them. This article is encouraging.

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  3. We don't have a bore (unfortunately) so we obviously haven't had to think of that. We did recently have our rented outdoor light from the power company removed and replaced with our own solar motion detector light. That was a good move, I'd like to add another and also a solar barn light in the milking room, but we have a lot of shade where they'd need to go!

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Thanks, I appreciate all your comments, suggestions and questions, but I don't always get time to reply right away. If you need me to reply personally to a question, please leave your email address in the comment or in your profile, or email me directly on eight.acres.liz at gmail.com

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