Selecting a solar water pump - new circulating pump technologies for solar hot water? - Page 4

Daox · 10-09-12, 06:54 PM

I got the pump and plumbing items from pexuniverse.com.

ecomodded · 10-09-12, 09:35 PM

It says Max. power input: 135 W , can you use half the amps for reduced consumption, if the pump is not required to lift the water 35 ft.
I'm curious what circulation rate gpm is used with a system like yours.
Seams like a powerful pump i guess you need the lift ?
With solar panels and a few batteries it could run it self.

Mikesolar · 10-10-12, 05:59 AM

Quote:

Originally Posted by ecomodded

It says Max. power input: 135 W , can you use half the amps for reduced consumption, if the pump is not required to lift the water 35 ft.
I'm curious what circulation rate gpm is used with a system like yours.
Seams like a powerful pump i guess you need the lift ?
With solar panels and a few batteries it could run it self.

A couple of pages ago, I suggested the Thermo-dynamics pump which is fed off a 20w PV panel. It is pricey but combines the variable speed with being totally off grid and a flow rate to match the hot water panels. He could have used 1/2" soft copper which is still more money than the pex but is easier to insulate and may have less heat loss than pex due to less surface area.

I have built many different types of systems from the micro-flow type which are popular here in Canada from T-D and another company (who shall stay nameless because I don't like them), to German system with high flow rates like Viessmann. According to the SRCC data, a T-D panel with a moderate selective absorber will be within 1-2% of a Sunearth panel with the same construction. The difference is the flow rate. The T-D is .4l/m/m2 and sunearth is .8l/m/m2 (These numbers are from memory so I may be off a bit). People concentrate on the panel and ignore the rest which is arguably more important.

The real difference is in how well you transfer that energy to the storage tank using a properly sized HX and matching the flow rates properly. It is almost like MPPT with PV, trying to find the best power output.

Since there are people doing Arduino and Raspberry projects on this forum, I think there should be solar controller project made for higher current pumps. There are controllers in Europe that take higher current but we tried to get on certified to a CSA standard a few years ago and gave up due to the pig headedness at CSA.

That said, I have been using a Taco 009 on drainback system with 4 panels with the RESOl controller (which is only supposed to take 1A) for 3 years now and the current draw is more than the Grundfos.

Daox · 10-10-12, 08:15 AM

Quote:

Originally Posted by ecomodded

It says Max. power input: 135 W , can you use half the amps for reduced consumption, if the pump is not required to lift the water 35 ft.
I'm curious what circulation rate gpm is used with a system like yours.
Seams like a powerful pump i guess you need the lift ?
With solar panels and a few batteries it could run it self.

If you look at the chart, you'll notice if you don't have 35ft of lift you simply get a higher flow rate. The purpose of the calculations I've done is to try to find the pressure head that you have at the flow rate you want, and then find a pump that closely matches those two variables.

In the case of solar panels, greater flow means greater efficiency by lowering the solar panel operating temperature and lessening the heat loss to the atmosphere. However, at some point your pump starts using more power than you gain from the efficiency benefit you see from the greater flow rate. So, you have to play a balancing act when trying to size your pump.

The post that Gary made has links to his testing of systems that show what flow rates returned different efficiencies, so that is the data I used to size my pump. I'd be interested in seeing any additional information that Mikesolar can provide that shows that a pump powered via a 20W pv panel is going to provide enough flow to efficiently operate these panels.

At this point I'm just trying to get the panels up and running. Solar PV is great, but there are many other things I would like to do to my home conservation wise (insulation mainly) that would be money MUCH better spent. Perhaps some day!

ecomodded · 10-10-12, 11:28 AM

What i meant was less volts not less amps, less volts would give you less amps and less flow, if you wanted a way to control the flow rate.
I must comment on the 20 watt pump, wow that is a tiny pump, a flow at 1/2 liter per sq m is required and the little pump does what 10 L per min?, how many sq ft room would the 20w pump be good for?, sorry my math is more then a little rusty so i'll leave it to those more adept at it..

Ok i just read some flow rates needed to move how many feet of water, i understand why you chose the 135w pump now ..

Mikesolar · 10-10-12, 06:20 PM

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Here it is. I'm not against your choice of pump, just that this is also available.

As the speed goes up on a circulator, so to does the head pressure so it is somewhat self limiting but if it is really an undersized pump, that circ will just spin way too fast without doing much.

Daox · 10-10-12, 07:36 PM

Sorry Mike, I don't see how that pump can get me up to the 5-6 gpm target I am looking to get. That flow chart only goes up to 3 gpm.

Daox · 10-18-12, 09:55 AM

So, I've been brushing up on my hydronics lately because of the solar project and also installing hydronic floor heating in my office. I was reading John Siegenthaller's 'Modern Hydroinc Heating' and happened to be reading the chapter on pump selection. He mentioned that it is quite common to find that, going from a PSC (permanent split capacitor) motored pump to a ECM (electronically commutated motor) pump will double your efficiency! This isn't even taking into account the benefit of the variable speed advantage that the ECM motors provide.

My Grundfos UP15-100f uses a PSC type motor. With a current draw of 135W, I'd be very happy to see something in the 65-70W draw as a replacement. So, I shall be looking into what options are out there for ECM motor pumps.

In the book, he continues on to show that a 85W pump operated for 3500 hours per year with an electricity cost of $.14 per kWh (a bit high) will uses almost $1400 in electricity over a 20 year life. So, reducing that number in half gives quite a bit of room for cost savings in a pump even if the new pump costs substancially more.

I've started a thread about PSC vs ECM pumps here: http://ecorenovator.org/forum/applia...find-them.html

Mikesolar · 10-18-12, 06:04 PM

About the pump speed......if you have a 100mbtu boiler which needs 10gpm to work properly, would you use 10 gpm on a 50mbtu boiler? No, you would use a 5gpm flow rate to get the correct dT.

The same is true for a solar panel, if it is less efficient because the technology is older or it is a less efficient absorber, you choose a different flow rate. This is why i talked about the T-D solar pump.

I am putting panels on my wall which have a painted (Solkote II) surface which is not as efficient as a highly selective absorber and I am using the T-D pump at the lower flow rate. This will give the liquid a bit more time to take the heat out of the panel for a bit higher flow rate. I though you would benefit from this pumps as well given the panels you have.

Daox · 10-18-12, 06:36 PM

How would you recommend figuring out the most optimal flow rate of any ol panel (be it new or old)? Could you make a setup where you put a thermal sensor before the panel and then after it, then adjust flow rate so that the temp delta was X degrees?

10-09-12, 06:54 PM	#31
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	I got the pump and plumbing items from pexuniverse.com. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

10-09-12, 09:35 PM	#32
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	It says Max. power input: 135 W , can you use half the amps for reduced consumption, if the pump is not required to lift the water 35 ft. I'm curious what circulation rate gpm is used with a system like yours. Seams like a powerful pump i guess you need the lift ? With solar panels and a few batteries it could run it self. Attached Thumbnails Last edited by ecomodded; 10-09-12 at 09:38 PM..

10-10-12, 11:28 AM	#35
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	What i meant was less volts not less amps, less volts would give you less amps and less flow, if you wanted a way to control the flow rate. I must comment on the 20 watt pump, wow that is a tiny pump, a flow at 1/2 liter per sq m is required and the little pump does what 10 L per min?, how many sq ft room would the 20w pump be good for?, sorry my math is more then a little rusty so i'll leave it to those more adept at it.. Ok i just read some flow rates needed to move how many feet of water, i understand why you chose the 135w pump now .. Last edited by ecomodded; 10-10-12 at 11:39 AM..

10-10-12, 07:36 PM	#37
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Sorry Mike, I don't see how that pump can get me up to the 5-6 gpm target I am looking to get. That flow chart only goes up to 3 gpm. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

10-18-12, 09:55 AM	#38
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	So, I've been brushing up on my hydronics lately because of the solar project and also installing hydronic floor heating in my office. I was reading John Siegenthaller's 'Modern Hydroinc Heating' and happened to be reading the chapter on pump selection. He mentioned that it is quite common to find that, going from a PSC (permanent split capacitor) motored pump to a ECM (electronically commutated motor) pump will double your efficiency! This isn't even taking into account the benefit of the variable speed advantage that the ECM motors provide. My Grundfos UP15-100f uses a PSC type motor. With a current draw of 135W, I'd be very happy to see something in the 65-70W draw as a replacement. So, I shall be looking into what options are out there for ECM motor pumps. In the book, he continues on to show that a 85W pump operated for 3500 hours per year with an electricity cost of $.14 per kWh (a bit high) will uses almost $1400 in electricity over a 20 year life. So, reducing that number in half gives quite a bit of room for cost savings in a pump even if the new pump costs substancially more. I've started a thread about PSC vs ECM pumps here: http://ecorenovator.org/forum/applia...find-them.html __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Last edited by Daox; 10-18-12 at 10:56 AM..

10-10-12, 06:20 PM	#36
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	Here it is. I'm not against your choice of pump, just that this is also available. As the speed goes up on a circulator, so to does the head pressure so it is somewhat self limiting but if it is really an undersized pump, that circ will just spin way too fast without doing much.

10-18-12, 06:04 PM	#39
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	About the pump speed......if you have a 100mbtu boiler which needs 10gpm to work properly, would you use 10 gpm on a 50mbtu boiler? No, you would use a 5gpm flow rate to get the correct dT. The same is true for a solar panel, if it is less efficient because the technology is older or it is a less efficient absorber, you choose a different flow rate. This is why i talked about the T-D solar pump. I am putting panels on my wall which have a painted (Solkote II) surface which is not as efficient as a highly selective absorber and I am using the T-D pump at the lower flow rate. This will give the liquid a bit more time to take the heat out of the panel for a bit higher flow rate. I though you would benefit from this pumps as well given the panels you have.

10-18-12, 06:36 PM	#40
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	How would you recommend figuring out the most optimal flow rate of any ol panel (be it new or old)? Could you make a setup where you put a thermal sensor before the panel and then after it, then adjust flow rate so that the temp delta was X degrees? __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.