Small scale solar & building mounted turbine for borehole pump

[Kentishfarmer]

I am thinking of installing some solar panels and a small building mounted wind turbine supplying a lead acid battery pack (cheaper than lithion ion) to power our pump for our private water supply. We've had a borehole and subsequent pump to pressurise our water supply network for 3 years now it has paid for itself already through water bill savings, but as were pressuring a pipework system over some distance and up steep inclines with quite a lot of water usage the pump is on pretty much constantly and so using a energy metering plug I've worked out it uses £2/day in electric so over a 4 year payback that gives me nearly £3000 to play with to build a renewable energy system. So its using about 35 KWh/units a day I think, and I was planning on buying a selection of Solar panels, an inverter, batteries and a small building based turbine to boost it throughout the winter online and then get an electrician to put it all together.
As you may have guessed I don't know much about the technical side of this and my solar panel experience so far only amounts to buying a panel of amazon and hooking it up to an old car battery to power electric fencing units.
Any advice from anyone greatly received, is there a formula to work out the size of the panels & batteries required? Is there a particular model of building mounted turbine known to be good? (the cheaper models look a bit flimsy) Or is what I'm suggesting even possible on that level of investment?
Thanks

 

[Highland Mule]

35kW-h / day suggests that the pump is around 1.5-2kW power. What height and distance are you pumping the water over, and what is the useage per day? It may be that the pipe would be better if it were larger bore.

 

[Kentishfarmer]

0.9KW by the look of it? There are a couple tanks in different directions where it has to pump 750 meters and another where it has an incline of between 50-60m from base (the installer didn't factor this in so we have to run it at 6.4bar to get it to pump it to the top of the hill 10m in altitude creates 1bar of back pressure I believe, he should have installed a pump with a larger headage) It can be watering up to approx 270 head of cattle and 3 houses which is probably why its working so hard. All the pipe work is 25mm once you get away from the 32 in the pumpshed. This is the distributor pump not the borehole pump that uses f**k all power but could run off the same renewable source perhaps.
So are you saying a bigger pump would save more energy?

 

[Doing it for the kids]

I’d say 25mm is a major problem for you, you will need more power to shove that volume up such a small pipe

 

[chickens and wheat]

Any other constant electrical use on farm? If so why not put decent amount of panels on a roof and tackle the whole bill not just the pumping element

 

[Kentishfarmer]

Any other constant electrical use on farm? If so why not put decent amount of panels on a roof and tackle the whole bill not just the pumping element

Unfortunately there isn't any other consistent electricity use on site and we can't put the excess into the grid and I'm not sure id want to anyway at 4p/unit. My understanding of renewables is they make financial sense if you use the eletric yourself hence a smaller system where we will use it all ourselves

 

[chickens and wheat]

yes little point gifting all the power to the grid, in your case

 

[Highland Mule]

0.9KW by the look of it? There are a couple tanks in different directions where it has to pump 750 meters and another where it has an incline of between 50-60m from base (the installer didn't factor this in so we have to run it at 6.4bar to get it to pump it to the top of the hill 10m in altitude creates 1bar of back pressure I believe, he should have installed a pump with a larger headage) It can be watering up to approx 270 head of cattle and 3 houses which is probably why its working so hard. All the pipe work is 25mm once you get away from the 32 in the pumpshed. This is the distributor pump not the borehole pump that uses fudge all power but could run off the same renewable source perhaps.
So are you saying a bigger pump would save more energy?

Okay, so if the pump is 0.9kW, then the most power it is consuming (assuming the sticker is close o being correct would be 0.9 x 24 = 21.6 units per day (slightly more today though, being as the clocks went back), so it's not quite as hungry as you were thinking. You can always stick a clamp ammeter on it to check if you want (Power = amps x volts), but bear in mind that if it's at the end of a long cable the voltage might be less than 240. Now you need to think where that power is going, and my bet would be mostly into frictional losses in the pipes, given that the distance is so long and pipes are narrow bore. As a rule of thumb, a wider pipe will need less push to get the same volumetric throughput. Unfortunately, the flow calculator doesn't recognise "cow" as a unit of flow, but it does feel like there's a fair bit going through it.

If you have any reason to dig up the pipe, make it a few steps bigger - for that use I'd be expecting way more than 25mm.

As to the solar demands for the existing pump, I can't offer any thoughts. You'd want a couple of days of hold-up for gloomy weather, plus auto switching grid backup, I'd expect, so maybe 50kW-h of storage? My latest car battery bought was 70A-h, I think, at 12V, so quite a bit less than one kW-h of storage. Gut feel tells me about 80 batteries, charged by enough solar to fill them in 4-6 hours, so 10+kW of panels. Doesn't feel like it's going to be easy.

All calculations done without access to fag packet, so my sums may be wrong - anyone want to sanity check them for me?

 

[delilah]

Welcome to visit (nr Ashford) and pick the brains of our PV guy who set this up to pump water and charge fencer batteries for us. We've not got the capacity you need but close enough to be relevant. We could sell you an inverter as we now have everything 12v.

 

[delilah]

ps. also got this setup which feeds into the grid for interest/ comparison.

 

[Kentishfarmer]

Okay, so if the pump is 0.9kW, then the most power it is consuming (assuming the sticker is close o being correct would be 0.9 x 24 = 21.6 units per day (slightly more today though, being as the clocks went back), so it's not quite as hungry as you were thinking. You can always stick a clamp ammeter on it to check if you want (Power = amps x volts), but bear in mind that if it's at the end of a long cable the voltage might be less than 240. Now you need to think where that power is going, and my bet would be mostly into frictional losses in the pipes, given that the distance is so long and pipes are narrow bore. As a rule of thumb, a wider pipe will need less push to get the same volumetric throughput. Unfortunately, the flow calculator doesn't recognise "cow" as a unit of flow, but it does feel like there's a fair bit going through it.

If you have any reason to dig up the pipe, make it a few steps bigger - for that use I'd be expecting way more than 25mm.

As to the solar demands for the existing pump, I can't offer any thoughts. You'd want a couple of days of hold-up for gloomy weather, plus auto switching grid backup, I'd expect, so maybe 50kW-h of storage? My latest car battery bought was 70A-h, I think, at 12V, so quite a bit less than one kW-h of storage. Gut feel tells me about 80 batteries, charged by enough solar to fill them in 4-6 hours, so 10+kW of panels. Doesn't feel like it's going to be easy.

All calculations done without access to fag packet, so my sums may be wrong - anyone want to sanity check them for me?

Very Useful information there, looks like I'd be needing more storage and panels than I had envisaged. Perhaps I could install a few £ks worth of panels & turbine to use the electric from when they are generating and then and then use the grid the rest of the time so reduce battery & total panel cost

I've found a couple of meter reads from 2 years ago subtracted the difference and /days comes out at 6m3/day I would have thought we'd be more than that at times. Also seen another reading on that pump label that says 1.34KW so could be that.

We were going to connect our supply up to another trough a few hundred M away across a road so we can remove the meter from there too. Would you recommend a pipe size even bigger than 32mm as we'd be putting it in new?

 

[Kentishfarmer]

Welcome to visit (nr Ashford) and pick the brains of our PV guy who set this up to pump water and charge fencer batteries for us. We've not got the capacity you need but close enough to be relevant. We could sell you an inverter as we now have everything 12v.

Thanks that looks exactly like the sort of thing, just with a little more power! I would like to come and have a look but I'm still recovering from a broken leg so cant drive/get around at the moment. Could I have the contact details of the installer? It would be good to talk to them

 

[gmgmgm]

Do you have a pressure tank and pressure switch (to turn on the pump) next to this electrical pump? Is it running constantly, or x hours in the day? If it's only running a quarter of the time, a lower-throughput (and lower power) pump may make more sense, as slower-flowing water will reduce your friction losses.

I suspect you will struggle to make batteries pay for themselves on this, but solar panels would probably be helpful to reduce the running cost. A system of 2kwh of solar panels could be a practical starting point for investigation. The optimum number/capacity could be worked out if you have the daily usage data. Keeping it "grid-tied" will be essential during the winter, as solar capacity drops to very small figures.

 

[upnortheast]

Have a play with this calculator to give a guide as to what sunshine will give you
Others available

Solar Power Calculator breakdown by month

See how much solar energy you will generate across the year with this monthly breakdown graph. Check to see if you are on target throughout the year.

www.in2gr8tedsolutions.co.uk

 

[Kentishfarmer]

Do you have a pressure tank and pressure switch (to turn on the pump) next to this electrical pump? Is it running constantly, or x hours in the day? If it's only running a quarter of the time, a lower-throughput (and lower power) pump may make more sense, as slower-flowing water will reduce your friction losses.

I suspect you will struggle to make batteries pay for themselves on this, but solar panels would probably be helpful to reduce the running cost. A system of 2kwh of solar panels could be a practical starting point for investigation. The optimum number/capacity could be worked out if you have the daily usage data. Keeping it "grid-tied" will be essential during the winter, as solar capacity drops to very small figures.

It's got a "speedomatic" digital pump controller which you set the pressure on, gaps between switching on in term of secs & pressure bar drop. So its not on permanently, its just the needs of the system mean its engaged pretty much the whole time, but it has longer gaps in winter when the stock are in and it doesn't have to pump to the difficult tanks.

Its got a pressure bladder too supposedly to take some of the pressure fluctuations but I think that should have been bigger.

I've read if your running direct off of panels without batteries then you can damage the pump due to power changes from too little/too much throughout the days production. But I guess there much be some controller/regulator/switch to stop this?

 

[gmgmgm]

Running off solar panels directly is not simple: you can't just connect up a 12v panel and 12v pump, for example. Better to go with a simple grid-tied 240v system and let the grid pick up the slack.

Good to hear you have the right controllers etc. You may be able to eke out some savings by reducing the max pressure (you don't want water squirting out of the ball valve in the tank, just flowing).

You mentioned it's "engaged pretty much the whole time" and "costs £2/day". But a 0.9kw pump running 24h would use 21.6kwh of power, which at £0.16p/kwh would be £3.46. So perhaps it's running much less than you expected? I suggest monitoring the power usage (kwh, not "cost") for a few days to see what the actual utilisation is, and to confirm the max power draw. Presumably this will be 0.9kw, and then you can size/cost the solar panels around this.

 

[Exfarmer]

If your water supply is critical and I rather think it is, do not go off grid. In winter there can be prolonged periods of low pressure , foggy damp days with little or no wind. Solar production then will be minimal too.
Thereis a golden rule with solar and that is 75% of production is in the months April / september.
and 75% of production is between the hours of 10 and 2 GMT
so you will have little power to recharge a battery system in winter
even last week a 50kw system of mine only achieved 200 units thanks to dull miserable weather, ie about 1/2 unit per installed kw of panels per day.
it is just Not economically possible to achieve The scale you would need to ensure continuous uninterrupted supply of water.
I have seen a recent model for predicting the efficient use of solar on a large site with a continuous draw averaging 500,000 units per year and the prediction was that it would not be effective to install a larger than 150 Kw array

 

[Kentishfarmer]

Thanks for the responses all useful knowledge I hobbled out to the pumpshed today and got some info off of my power usage recording plug it is using 13.3Kwh/day since July on our current tariff of 18p/unit that's £2.40/day. Which shows me that I cocked up my previous calculation, knowing it was costing about £2/day I multiplied that by 0.18 rather than Divided to get the KWh usage, f**king Idiot!

Took another water meter reading and worked out daily consumption over the last 2 years averages at 6.75m3/day. If your interested 6.75m3 X £2.055 (CWs retail & water costs per M3) = (£13.90/day saving - £2.4/day electric) X 365 = Approx £4187/year saving from having a borehole over mains. Just got to reduce the £876/yr electric cost now!

I've included the photo of the readings below incase I've interpreted it wrong. The amp reading was 4.5 Then I've got 3 readings W (assuming watts) 630 and then W low is 1.4 W high is 1074? how does this factor into the power = Amps X watts?
V= 240.6

Having looked at the solar power breakdown calculator I think a 3KW system would give me all of the KWh requirements for a good number of months/year, obviously I have to take into account that a portion of the demand is going to be happening at night. I think I'm going to buy an anemometer to measure the wind speed on top of the building to see if a turbine would be worth while to get a portion of the energy from that.

One of the big components of the system that I don't really understand will be some sort of power controller that switches the pump from mains or solar/wind. What happens when the renewable is only generating say half the output required to run the pump? Does it then use 50% mains 50% renewable or does it have to switch fully to mains?

 

[gmgmgm]

Thanks for the responses all useful knowledge I hobbled out to the pumpshed today and got some info off of my power usage recording plug it is using 13.3Kwh/day since July

That's useful to know- versus the maximum possible power consumed of 21.6kwh in a 24hr period, you're running at a duty cycle of 61%. So you have spare capacity. And you will need a lot of solar panels to make a dent in that figure during winter!

One of the big components of the system that I don't really understand will be some sort of power controller that switches the pump from mains or solar/wind. What happens when the renewable is only generating say half the output required to run the pump? Does it then use 50% mains 50% renewable or does it have to switch fully to mains?

This is actually the easy bit. Any "grid-tied" solar panel "inverter" (box between panels and mains) does this for you automatically. When there is lots of sun, the inverter makes sure the system (pump, house, whatever) takes the free solar electricity first. When there isn't enough, power comes in from the grid. It's totally transparent in use, and there are no switches. Any excess would either go back into the grid as free power for the utility company, or go to other consumers in your house/farm. Hence why you could put in a large or small set of panels e.g. 0.5 kw of panels or 4kw+. If you put in a small number of panels then the free power will always go to the pump, topped up with grid power. If you put in a large number of panels then sometimes you'd be running purely on free solar power, but other times you are giving away free energy. You can see there will theoretically be a "sweet spot" where the free power balances with the cost of the panels.

 

[blackisleboy]

Why not use a smaller solar/battery set up, and integrate with a variable electric tariff. The battery powers the pump for the expensive tariff hours, but mains does it for the 'off peak' hours. And the mains is there when it isn't sunny or windy......

I would have said that at £2.40 per day for water to 3 houses and 200 odd cattle you were doing it at low cost anyway. Surely there are other bigger savings to be had elsewhere in your enterprises.