Off-Grid Chiller Unit?

[russ]

I have considerable experience with new stuff - I have a few patents in my name and my name as one of the et all on others. All related to the iron ore direct reduction field. We did things in the plant when the technology supplier was still discussing whether it would work or not. Sometimes it works out and sometimes it is a flop.

A lot of things that can be cost effective in the states are either not available here or overly costly. Competition is a wonderful thing! Wish we had more of it!

I would now prefer the VRV (what multiple outlets with one compressor are called here) for flexibility, cost of operation and simplicity. With the water to air heat pump (5 ton) there is a minimum water flow through the unit - there should be a control valve and a recycle to short circuit the hot water (I run my water temperature at 38

[HotFlash]

Russ, I would think cooling a floor in the summertime would result in sticky/sweaty floors. Well, at least that would happen around here. We really live in a soup.

I figure we need a room temp/coil deltaT of about 20F to keep RH down to around 50%. Higher than 60% (deltaT of 15F), and we start having mold problems. That said, we seem to live with a summertime RH around 80% in this old house (the one we're moving out of). Mold is a problem, but with sunlight it's slight. Lens fungus (I'm a photographer) is a huge issue, but I've long since worked out humidity controlled storage solutions. Overall, we manage to live with it. We normally keep the house around 80F in daytime and 77 at night during the summer. This would correspond to marginally OK coil temps of maybe 70F and preferable coil temps of maybe 57-62F. This all assumes perfectly efficient heat exchange, and I recognize that's one of those "impossibles." I think a good, workable coil temp might be 50F, and I feel that could be an average between daytime and nightime.

The ducted forced air hydronic heat exchanger I'm describing is perhaps not what you're envisioning. I think you're imagining a central system with motorized valving/registers to open/close air passages. Instead, I'm thinking of a separate air handler for each zone, each with its own thermostat. Three zones (our core, office, and bedroom) would have programmable thermostats, and the rest would be conventional ones that we would manually set according to usage requirements (e.g. guests). Simply, heat/cool is distributed when the thermostat turns the fan on. Water flows through the entire system whenever there is a demand in any zone. No complicated valving -- all electrical/electronic. I've contemplated, and might ultimately build, thermostats that drive the fan motors proportionally, so as to keep air delivery continuous and minimize noise.

Wood: Free and WAAAAY too available! We have hurricanes here. We've got a load of Hurricane Irene wood in the back yard (some nice pecan) that is ready for splitting and stacking. We've tried giving it away, but everyone who burns wood is already stacked to the gills. As it is, we already lumbered the trunks and have approx 3000 board feet of pecan, ash, and curly maple drying. Most of our Hurricane Isabelle wood is still lying in the woodlands, rotting away. Anyway, a wood furnace would be a great way to get rid of everything that falls (exception for pine). As it is, we're always throwing our wood away at the dump. It gets shredded for mulch, of which we have too much. It seems such a waste. Perhaps wood is our "Plan C," as we could certainly sustain our house on that alone. It's just that wood has aptly been described around here as "another part-time job."

[russ]

There is tubing in the floor for heating and the fan coils for cooling. Cooling behind or under a surface is rarely a good idea. A different contractor tries to sell me that as well.

Your 'separate air handler for each zone' is called fan coils - water is piped to each fan coil.

Daikin makes one of the best ASHP producing chilled water today.

[HotFlash]

Dereck, I have to laugh, because I'm reminded of a joke from an old war movie (?). Everyone was raving over the uncharacteristically good dish that some Army cook made that he claimed was an old family recipe. His father was an Army cook, and so was his grandfather. Someone asked him if he would share the recipe, and he said, "Sure! You start with 14 gallons of tomato sauce, 5 large hams...." Maybe that's where we're failing to connect. I'm not talking about driving a 5 ton 220VAC unit off of an 800W UPS, nor am I trying to recreate any of the massive systems that you apparently deal with. Think much smaller:

Let's say I have a 500W patch of PV on the rooftop (not the entire system -- just talking about 500W of it) that I'm happily dumping into the grid, and one day I'm told net metering is no longer allowed or has been made financially problematic because of arbitrary fees. I then have the following choices:

1. Bow to the will of the utilities, and surrender all my power to them for free.
2. Abandon the 500W patch of PV rooftop and let it rot.
3. Pull the PV panels from the roof and sell them to someone where net metering is still done.
4. Figure out some other way to use that 500W patch of panel, even if it's not the most efficient use.

I would explore option #4, which is the purpose of this thread.

One idea that has occurred to me is to feed the 500W patch of panel into a charge controller to keep a battery topped off. Invert power from that point to drive the compressor from a little (e.g. 5000 BTU/hr ?) window AC, which would be used to dump heat from the thermal mass to the coil on our dock. Then repeat this several times in parallel. This would be useful -- maybe not optimal, but still useful. (But we don't need 5 tons for this house! At night, a small window keeps us blissfully comfy right now, in the middle of summer.)

Although there is loss in efficiency from this double (vs. single) conversion strategy, I doubt it would waste 50% of the energy. By contrast, I would have to approximately double the ratio of panel to cooling load just to overcome the LRA on compressor startup without a battery and oversized inverter to assist. Maybe there's an alternative strategy to starting a compressor on a limited supply???

If very short term storage can't be done (which I think it can), then we could still start up a 500W compressor unit on roughly 1kW of panel. Less useful, but still better than nothing.

And does this system have to run 24/7? No. Let's say we have a cloudy week. Then we draw from the grid like respectable folks and pay Dominion the money they so richly deserve. However, when there's sun, we've reduced our electric usage. Useful, yes. Optimal no. Better than nothing. Understand where I'm going?

[HotFlash]

Rich, I realize I'm talking to a bunch of engineers, and there are probably a number of small issues that I'm aware of but don't have the knowledge to address with all the elegance that a commercial, for-sale system would have. However, if you step into my shoes for a moment, as a (now) professional photographer, perhaps I can make you understand. Let's say you wanted photographs for your website, which I've visited. You have the option of hiring me (or someone like me) who is a very skilled professional, hiring one of the hoards of late-comer "professional" hacks, or doing it yourself. If you were to hire me, I would do all sorts of things that would never occur to you (and indeed wouldn't occur to most other pros) to make your photos come out fantastic. Then you would pay me (fairly well) for my skill and expertise. This doesn't negate the fact that you could also take your own camera (probably not nearly as good as mine, but possibly even better) and take a useful and serviceable, albeit not great, photo yourself. It seems likely you've taken the latter option (as do most people these days). You've decided that the refinement I can offer you is not worth the price. I can't fault you, because I might decide the same thing in your shoes.

Skipping to solar, I realize I could throw a boatload of money at a turn-key installation of very refined products currently in this niche market, but I don't have tens of thousands of dollars to blow. What I have is my two hands, my mind, lots of tools, and some determination. My system might not end up a thing of great refinement, but if it works, I'll be happy.

And can I do it? I look at the various HVAC systems that I've had in my lifetime, and the very best one I've ever had is a 2.5 ton system I designed and installed myself -- in a 1500 sf garage and upstairs apartment I designed and contracted/built myself. I bought the unit via the internet, farmed out the ductwork to a metal fabricator, and paid a licensed HVAC contractor make the final freon line connects, charge, and fire up the system (per law and warranty terms). The HVAC contractor complimented me on my work. Total cost was $2200. This was roughly a quarter of what the pros quoted, and it wasn't really hard to do the work. What would the pros have done? Most HVAC contractors just throw a big unit in the house, string ductboard and flex duct all over the place and call it good. Half of the time the system doesn't work particularly well.

While I might not get all the refinements exactly right, I'm pretty sure I can make a system work well enough for our purposes. For instance, although I might design for a week's winter heating without sun, based on a number of estimated factors, I might only get a few days -- or even two weeks. That's probably not close enough for an engineer, but it's close enough for me. If I don't get it right, I can always modify, and in the event I'm totally wrong about something, there's always emergency firewood heating or temporary window unit cooling until I can get the system straight.

Anyway, I guess that's where I'm coming from. But hey, if you and your colleagues want to pay me lots of money for my photographic work, perhaps I'll have lots of money to spend on a turn-key system. Meanwhile, if you show up on PhotoNet and ask for free photographic advice, I'm likely to give it to you -- probably for the same reason you're here giving advice to me. And then we'll both seek out our own DIY solutions. I guess that's how it all works in this awful economy. (Here's hoping for better times ahead...)

[HotFlash]

Thanks, Russ! Daikin water-cooled water chillers. Nice!

[HotFlash]

But Rich, your point is well taken about partitioning up the thermal mass. I'm envisioning two partitions. The much larger one will be for wintertime heat, and the much smaller one will be for summertime cooling. Perhaps I'll even make that a small-ish stand-alone tank with better insulation than the huge concrete baths. It woudln't make sense to chill a huge reservoir off of grid power when no long-term storage is required.

As for the Plan B, I'm thinking maybe 1/4 of the larger concrete structure could be partitioned off for off-grid cooling (if it later becomes necessary). That 1/4 could be used in combination with the 3/4 for wintertime heat.

[Naptown]

Sarah
Let's get one thing straight. I am not trying to sell you anything. Although we are licensed in VA you are so far away that it would be not in either of our interests to pursue a "sale".
What I and others are trying to do is prevent you from spending a whole lot of your hard earned cash on things that may or may not work, or only work marginally.
From a cost effective standpoint a self installed ( And you can do this in most of VA) grid tie system of all UL listed components would give you the greatest return on your investment.
Batteries are fine as long as you realize that you are adding a substantial amount to the original install cost and Like heating with wood another part time job maintaining a very large battery bank. And that battery bank would need to be replaced every 5 years or so. Probably sooner until you go through the learning process of how not to destroy your batteries, Most people will destroy their first set.

[Naptown]

But Rich, your point is well taken about partitioning up the thermal mass. I'm envisioning two partitions. The much larger one will be for wintertime heat, and the much smaller one will be for summertime cooling. Perhaps I'll even make that a small-ish stand-alone tank with better insulation than the huge concrete baths. It woudln't make sense to chill a huge reservoir off of grid power when no long-term storage is required.

As for the Plan B, I'm thinking maybe 1/4 of the larger concrete structure could be partitioned off for off-grid cooling (if it later becomes necessary). That 1/4 could be used in combination with the 3/4 for wintertime heat.

This is important as A) if you don't have cold enough water you will have a cool humid home with humidity higher than outdoors.
B) temperature differences between indoors and outdoors are not as high during the cooling months as they are in the winter and less mass (BTU's) would be needed.

[HotFlash]

Rich, I'm sorry... I left the wrong impression. I'm wasn't trying to suggest you were trying to sell me anything. Rather, I was just saying we come from two different perspectives. You deal in all the expensive, refined equipment, and all discussion by you and others has been pitched within the framework of this equipment. I'm just trying to break out of the box. That's all. It's just like when you and I use the words "nice camera," we probably mean something entirely different.

[HotFlash]

with humidity higher than outdoors

LOL Physically impossible! But point taken! Yes, I'd love to knock down the humidity in my living environment. I'm tired of my humidity cards being solid pink.

[Naptown]

LOL Physically impossible! But point taken! Yes, I'd love to knock down the humidity in my living environment. I'm tired of my humidity cards being solid pink.

Absolutely possible and will always happen.
If you take air at 80 degrees and cool it to 70 degrees without removing any of the moisture what happens to the relative humidity? It goes up! Physically absolute. keep cooling it and eventually you will have fog then rain.

[HotFlash]

Rich, from a practical standpoint, what is the importance of the UL certification? Is it to keep me out of trouble with regard to insurance claims? Do insurance companies disallow (not sure what the term is) claims where non-UL-certified devices are involved?

[HotFlash]

Rich... I was joking. You start with 100% RH southern VA coastal air, drop the temp, and you have a lot of condensation + 100%RH air. Although the RH isn't *really* 100% all the time, sometimes I feel like it is.

[Naptown]

Rich, from a practical standpoint, what is the importance of the UL certification? Is it to keep me out of trouble with regard to insurance claims? Do insurance companies disallow (not sure what the term is) claims where non-UL-certified devices are involved?

every time. There was a case where someone had a fire that was unrelated to a non UL listed item and the insurance company once they caught wind that it was there denied the claim. read your policy veeeerrrrryyyy carefully.