Solar Pool Pump (3-phase DC vs VFD AC)..need help with decision

Re: Solar Pool Pump (3-phase DC vs VFD AC)..need help with decision

Welcome to the forum ArmyChief!

The forum is a community based on all of the posters here. Everyone brings something different and it is a joy to read (and the little moderation we ever need to do makes it pretty easy. Mostly just spam patrol).

I think you are on the right track looking at ROI.. Just make sure you include maintenance costs too. Electronics will need replacing every ~10 years, many times because repair parts/services are not available after 5-10 years (at least have the funds in the bank so no surprises).

Next, are you looking at doing the pump with off grid inverters and battery bank? It almost always costs a lot more for off grid power vs utility or grid tie power (usually around $1-$2+ per kWH when initial costs and down the road replacements are included--10 years for electronics, 5-10+ years for batteries, the extra losses from battery+inverters give you a ~52% end to end efficiency from solar panel spec to AC power vs ~77% for a Grid Tied system--Plus solar, of both types, does give you the 30% federal tax break--for now).

Grid Tied solar, cheaper, more reliable, less service -- Does have one major down side, no power if the utility power/grid is lost. Still need generator and/or other solar power system for emergency power (there hybrid "hybrid" GT inverters which can be somewhat more cost effective if you need emergency power--but still expensive to install).

Regarding you water heater... Assuming you need A/C much of the year (cooling/humidity control), look at heating systems that take the energy from your central air heat pump--Or even a stand-a-lone GE or other brand heat pump water heaters. Will be about 2-3 times as efficient as standard resistance heating, and cooling the room and dehumidifying are the "side effects" of generating the hot water.

One poster here believes that a Grid Connected heat pump water heater is a better long term deal than solar hot water (pumps, tanks, thermal collectors, leaks, complexity, debugging, etc.).

Anyway--A little more about your power needs and what you are looking for (saving money, emergency backup power, going green, getting off the grid, etc.).

In most cases, "extreme conservation" is cheaper than generating your own electric power. In some cases, having a Grid Tied solar power system can be a wash or even same money vs grid power (in my area, summer peak "time of use" rates are around $0.30 to $0.50+ per kWH, and GT solar cost me around $0.15 per kWH). But much of GT solar depends on your local rates and the billing plan supported by your utility. Mine, I get 100% retail payment for anything extra I get (credit to bill, not cash). In some areas, you will be credited for the wholesale cost of electricity--Which can be down to the $0.05 per kWH range.

-Bill

Re: Solar Pool Pump (3-phase DC vs VFD AC)..need help with decision

The GE water heater (and other brands) is an electric water heater with a refrigeration compressor and condenser mounted on top of the tank.

And the new air sourced a/c systems are efficient enough to maker ground sourced systems not worth the costs.

Check with your local utility about their gt solar rules. That can make or break the gt install.

-Bill

Re: Solar Pool Pump (3-phase DC vs VFD AC)..need help with decision

We are more than happy to discuss the technical ins and outs of solar power (GT, off grid, hybrid, etc.).

But the whole Utility/State PUC thing is a serious issue. Some places it is very straight forward. $5 per month billing/minimum charge. At the end of 30 days, read meter. If "positive", pay the normal bill. If "negative" (meter spun backwards), credit the money to account and pay the difference (or pay after 1 year the net power used, if net credit in bill, account is set back to zero and billing starts over).

If you install a GT system without utility approval... They can "ask you" to remove the system, have your home red-tagged, many "new digital meters" will read "forward" when the power is being fed back to the grid (i.e., you generate excess power, then you pay retail for that privilege). This was because in the past, customers would install meters upside down for part of the billing cycle to run the meter backwards (theft of power).

In California, we had the situation for awhile where people were forced to Time of Use billing--and if they installed a small GT system (to try it out)--Their bills actually increased.

But, in general, solar GT power can, for many people, equal the cost of utility power, and for some (with tiered power rates were we pay more as we use more power), it can save significant amounts of money.

-Bill