On Demand DHW Solar-ASHP Hybrid - Page 2

AC_Hacker · 01-06-12, 04:10 PM

Quote:

Originally Posted by Xringer

I've seen a few car AC systems that worked almost instantly. I know my Sanyos can start making serious heat within about 90 seconds...

There's a really big difference between a puff of air warming the surface of your skin and raising the temperature of a 40 gallon tank 40 degrees (8.35 x 40 x 40 = 13360 BTU).

A propane demand heater could give you water really FAST because it fires to a temp of several hundred degrees. You HP is lucky if it hits 130F.

You would be miles ahead if you used a HP, sized so that it would barely do the job, for preheat (solar addition, too) and finished the temperature lift job with a propane or electric demand heater (like Daox has), if required. Ebay has scads of little propane demand heaters.

-AC

Xringer · 01-06-12, 05:47 PM

Thanks Student 07,
I have a lot of ideas about controllers but, I think the CAI board has got a lot of
the bases covered in this type of app. IIRC, AC_Hacker has also started working on the CAI board.
I'm sure we he's going to show us what CAI can do as a controller.
(My CAI app is mostly about status monitoring).

I've been reading these comments about the raw heating power needed for quickly heating water,
And it is smarter to heat slower/longer with a lower powered HP.
(Like the Rheem EcoSense does it).

So, I'm getting more interested in trying to build my very own cheap copy
of a Nyle Geyser unit.

I won't be getting any solar hotwater panels (not allowed on roof anymore),
but I would like to try heating up my old 76gal boiler with in indoor ASHP.
(This is how desperately I want to get away from burning oil)..

I have a couple of small ACs in the 6k range and the old 230v 18k that
could be used for a project.

I beg to differed on PV compared to solar HW collectors for heating DHW.
I've worked with both ways now, and solar HW collectors would
be much better than direct PV heating of DHW. (And cheaper too).

PV is very much effected by any kind of shadow or blockage.
Just a few leafs sticking on the PVs can cut their output by half..
The same blockage on a HW panel would hardly be measurable.

PV of DHW has no moving parts and will last decades longer, but it's cost is too high so far.
PV-DHW will be a Go, when PV is 35 cents a watt..

Student 07 · 01-06-12, 09:52 PM

Hi,
Xringer it sounds like you need a Daiken Altherma ASHP. I have been looking at them but they are very expensive ($18,500), at least for me

The nyle geyser would take a long time to heat 40gl or even more to heat 76gl of water. But, I guess if you're patient enough, eventually it would heat the boiler.

I was contemplating a larger system for ASHP water heating. I was looking at a standard mini split ODU (Mitsubishi, Sanyo-?) with a hacked IDU.

The Daiken uses a "Hydro box" for an IDU. I found out the "Hydro box" contains a heat exchanger, circulating pump, air vent, expansion vessel, pressure relief valve, strainer, and an electronic controller.

A heat exchanger for a heat pump heated spa would work. Aqua source has one that is rated at 12,000 BTU, they can always be connected in parallel for larger requirements. The rest of the stuff is basic and can be bought "off the shelf", except for the controller. I am sure it would be possible to hack a controller, but I have no idea what information the ODU needs.

As far as the PV question goes: I think you're right and a solar thermal system would outperform a PV electric heater setup, but would it out perform a PV HP setup? If the hp had a COP of 3 the PV could be 1/3 the size to get the same BTU output.(?) Then again, if you compare them on an economical basis, the solar thermal would win.

I always heard the PVs still operate when cloudy, but at a reduced output.
Our DIY PV System Two Year Update

under Impressions he wrote:
"While the solar electric systems are not nearly as efficient under sunny conditions as solar thermal system (it takes 3 or 4 times the collector area of PV collectors compared to solar thermal collectors to make the same amount of energy), it is impressive how PV panels continue to generate some power (albeit not much) even under difficult conditions. Long after the solar thermal panels have stopped producing any energy the solar electric panels are still trickling out some power."

To me, some is better than none, especially with our weather.

This guy also did a great experiment showing how shadows affect PVs output.

Anyway, with everybodys input and help, I am sure you will be able to "fine tune" the details of an awesome heating system. EcoRenovator is a great resource.

01-06-12, 05:47 PM	#12
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Thanks Student 07, I have a lot of ideas about controllers but, I think the CAI board has got a lot of the bases covered in this type of app. IIRC, AC_Hacker has also started working on the CAI board. I'm sure we he's going to show us what CAI can do as a controller. (My CAI app is mostly about status monitoring). I've been reading these comments about the raw heating power needed for quickly heating water, And it is smarter to heat slower/longer with a lower powered HP. (Like the Rheem EcoSense does it). So, I'm getting more interested in trying to build my very own cheap copy of a Nyle Geyser unit. I won't be getting any solar hotwater panels (not allowed on roof anymore), but I would like to try heating up my old 76gal boiler with in indoor ASHP. (This is how desperately I want to get away from burning oil).. I have a couple of small ACs in the 6k range and the old 230v 18k that could be used for a project. I beg to differed on PV compared to solar HW collectors for heating DHW. I've worked with both ways now, and solar HW collectors would be much better than direct PV heating of DHW. (And cheaper too). PV is very much effected by any kind of shadow or blockage. Just a few leafs sticking on the PVs can cut their output by half.. The same blockage on a HW panel would hardly be measurable. PV of DHW has no moving parts and will last decades longer, but it's cost is too high so far. PV-DHW will be a Go, when PV is 35 cents a watt.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

01-06-12, 09:52 PM	#13
Student 07 Helper EcoRenovator Join Date: Dec 2011 Location: Gresham OR Posts: 35 Thanks: 0 Thanked 3 Times in 3 Posts	Hi, Xringer it sounds like you need a Daiken Altherma ASHP. I have been looking at them but they are very expensive ($18,500), at least for me The nyle geyser would take a long time to heat 40gl or even more to heat 76gl of water. But, I guess if you're patient enough, eventually it would heat the boiler. I was contemplating a larger system for ASHP water heating. I was looking at a standard mini split ODU (Mitsubishi, Sanyo-?) with a hacked IDU. The Daiken uses a "Hydro box" for an IDU. I found out the "Hydro box" contains a heat exchanger, circulating pump, air vent, expansion vessel, pressure relief valve, strainer, and an electronic controller. A heat exchanger for a heat pump heated spa would work. Aqua source has one that is rated at 12,000 BTU, they can always be connected in parallel for larger requirements. The rest of the stuff is basic and can be bought "off the shelf", except for the controller. I am sure it would be possible to hack a controller, but I have no idea what information the ODU needs. As far as the PV question goes: I think you're right and a solar thermal system would outperform a PV electric heater setup, but would it out perform a PV HP setup? If the hp had a COP of 3 the PV could be 1/3 the size to get the same BTU output.(?) Then again, if you compare them on an economical basis, the solar thermal would win. I always heard the PVs still operate when cloudy, but at a reduced output. Our DIY PV System Two Year Update under Impressions he wrote: "While the solar electric systems are not nearly as efficient under sunny conditions as solar thermal system (it takes 3 or 4 times the collector area of PV collectors compared to solar thermal collectors to make the same amount of energy), it is impressive how PV panels continue to generate some power (albeit not much) even under difficult conditions. Long after the solar thermal panels have stopped producing any energy the solar electric panels are still trickling out some power." To me, some is better than none, especially with our weather. This guy also did a great experiment showing how shadows affect PVs output. Anyway, with everybodys input and help, I am sure you will be able to "fine tune" the details of an awesome heating system. EcoRenovator is a great resource.