Dump the plumbing and use PV to heat water?

[AirSepTech]

If your calcs are right, I say yes--4100btu/h x 5 =20500btu

I use 13500btu/day for hot water. I could use less. 1 shower, couple handwashes, kit.sink use, 1 person. Goes up when the honey is here, not much, it is totally up to her.

I am gone 12-14 hrs/day, and 2 weekends a month. Work, you remember, right? hahaha

I have a 50g elec. heater, 4500w limited to 2, 1 hour events a day. It almost always cuts out before 1/2hr run time. Set for am/pm, I use right after the on cycle, always enough. Over-ride is a pushbutton, you know, when the guests are wasting your hard work.
I am limited to elec(.085kwh) or LPG($3 gal.). LPG at 100% eff. (not possible) would cost more, and the hardware even more yet. Thats stupid.
I am all ears about your project.

[Xringer]

I'm starting the 250 watt heater smoke test today.
It's installed on the boiler and all should be running 24/7 for a week or two.

http://ecorenovator.org/forum/applia....html#post6094

It seems stable at 246 watts (839.38 BTUh). I'll keep an eye on it tonight, just in case it over-heats the boiler..
(Not likely). Both smoke alarms test ok.


Anyways, the reason I'm wasting energy is to simulate the heating power
I would get from a very small PV array. (If I every buy some panels).

Once I see there that 839.38 BTUh is actually more than the heat loss
and is actually enough to save a bit of oil, I'll switch the heater to a timer
and only apply AC power for 5 hours a day.. And see how that works for me..


One of the things that got me interested in better insulation of my boiler,
replacing the mixer and PV solar assist, was a post I read somewhere
about just using the pilot light on a gas water heater.
I was amazed that anyone could heat their hot water tank with just a little pilot light.
Edit: Found it! Water heating using ONLY the pilot light - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com


I'm planning an experiment as I type this.. I'm going to turn off the oil burner and observe the rate of loss in the boiler.
(With the hot pad on).
If I can keep my wife from using any hot water for a while, I can get some interesting data..

[AirSepTech]

"If I can keep my wife from using any hot water for a while" ????????

Thats an easy fix, throw her the car keys and a credit card, you'll have all the time you need!!!

Seriously, this is a good test. The Alpha/Beta/commisioning trials of anything are a challenge. I get the comm phase at work, not much fun sometimes. The home stuff is fun, and keeps you out of trouble.

Best of luck to ya

[Xringer]

Turns out, I have seen the enemy and I am him.. After starting up the test,
I went to wash up and automatically turned on the hot water..
(And I know it would take 30+ seconds to get to the bathroom).

So, I went back down to the basement and pulled down the Hot water cut-off..

The long range forecast is looking like we are going to need some heat
during the next few weeks. But, not a lot. I should be able to cut the
min-max temp of the boiler down 8 or 10 degrees and still have
pretty good baseboard heat..
Next month, I'll be able to lower the average temperature of the boiler
down to about 120 to 130 degrees F.
I think that's when I'll really find out if 250 watts does anything..

[Xringer]

The boiler didn't drop or gain a degree between 1800 and 2200 hours.
The gauge stayed at 162 F and the temperature probe placed just
under the top cover stayed at exactly 100F for the whole 4 hours.

I once did an over-night loss check on the boiler and found it had
a loss of between 2 and 3 degrees per hour.
I'm not sure if that was before or after I did the last insulating job..

IMHO, without the 240-250 watt heater, the temperature would
have dropped at least a few degrees in 4 hours.



Equilibrium. So, this is good news. There is room for improvement.
A couple of things can be done without incurring much cost.


1. Increase insulation.

2. When it gets warmer outside, lower the Aquastat setting to 130F max.

3. Install the new mixer when it comes in next week. (Ebay).
The mixer will really help during the winter when the boiler is at 180F..

Once 1 & 2 are done, I suspect there will be a net heat gain, if the heating pad is left on 24/7.
But, that gain will be canceled out or go negative, once I put the heating pad on a 5 (or 6) hour timer.


The solar tracker mount seems to be seeing good sun starting at 11:00 (tree blockage)
and starts losing it around 16:30-17:00.
I'll have to take a new look at it now that we set the clocks ahead..

[Xringer]

We're getting good sun on the tracking mount between 10:30AM & 4:30PM
I'm thinking that 6 hours of good PV power will do the trick.

I retested the 250w heating pad on the boiler today and got some good results.
Time: Main: Upper:
13:00 148F 110F
15:00 152F 128F

At these lower boiler temps, It looks like a 2 deg-per-hour increase
on the main gauge and a 9 deg-per-hour under the upper cover.

During a sunny 6 hour day, (if no hot water was used) the main storage could possibly pick up 12 degrees,
if I was using a 250w PV array into a resistive HW heater!

I'm thinking that 240 to 300 watts of PV would be a good match to
my boiler, since it might coast some into the evening hours, before
the oil burner would want to kick in again..

All bets are off, if the dishwasher is used or someone takes a shower..

But, over-all I suspect there will be some reduction in oil use.
Especially during very sunny days when there is minimal hot water use..

If I we had went on a road trip this weekend, (using zero hot water),
that burner is going to keep on running when the loss builds up.
It's going to cycle once or twice a day.

Pay back? Break even? Not a concern with this project..

[Xringer]

Been dreaming of some of the smaller PV panels for this hot water idea..

Two of these ($707 shipped) would fit the tracker with some room to spare..
120w solar panel, solar module 120w

* 36pcs of 156x156mm multicrystalline solar cells (made in USA)
* Pmax: 120W
* Vmp: 17.6V
* Imp: 6.81A
* Voc: 21.82V
* Isc: 7.46A
* Size: 58.27"x26.61"x1.97"
* Weight: 28.3lbs
* UL, TUV and CEC listed

I'm just wondering what would be the best way to deliver the max amount
of juice to the heating element in the boiler.?.

I've been thinking about using a 12V load resistance (~0.6 ohms), driven by one of those BZ MPPT250HV 25A,12V
Maximum Power Point Tracking (MPPT) PV Charge Controllers..

Solar Cell, Solar Panel, Solar PV, Solar Products, Charge Controllers, Solar Trackers - BZ MPPT250HV 25A,12V for Higher Input Voltage

But instead of charging a battery, it would be trying to deliver max amps at 12 volts into a load.?.

OR, just use the less complex plain resistive load.

Comments please..

Thanks,
Rich

[Daox]

Unless you need to store the energy for later use I'd think just a plain 'ol resistive load would be most efficient.

[jwxr7]

I'm in a similar situation, but my boiler burns propane. In the summer the only thing the boiler does is heat our hot water via an Amtrol boilermate system.

I like this idea you're working on. No moving parts or added plumbing is definitely worth something over efficiency.

Using an mppt or buck-boost converter circuit is a great way to get the most out of your panels. I was thinking about trying to build a buck-boost converter to play with, maybe implement it into small scale wind power. That way power that is produce under light winds (below the voltage required to do whatever I intend it to do) can still be put to use.

[Xringer]

Originally Posted by jwxr7

No moving parts or added plumbing is definitely worth something over efficiency.


Using an mppt or buck-boost converter circuit is a great way to get the most out of your panels.

I think many people look at PV efficiency / payback etc. totally based on today's kWh cost from their power company.

I need to compare the cost of BTUs I can put into hot-water (using PV),
with my cost for home heating oil. That oil isn't real cheap these days.

In my case, the BTUs contained in a gallon of oil is somewhat irrelevant, because of the large
amount of BTUs my oil burner just shoots up the chimney, and just plain old heat loss.

Right now, Diesel Fuel is $2.84 to $3.36 a gallon around here. Home heating oil will be very close to the same price.

If the cost of PV was $800, that would be equal to about 260 gallons of oil.
IIRC, my tank holds 275 gallons of oil..

I'll bet you are incurring significant loss heating summer-time hot water with a whole house heating system too..

~~~
I'm not sure how much would be gained with power-point-tracking vs. just hooking up the best possible matching load.
Perhaps, if it's not too costly, I can start off with just a plain resistive load and see how well it works..

I've pretty much sold myself on the idea of just running 240 watts of PV..
That would make it a bit easier to handle the power level and the hardware.