Coal in a hard place.. expecte to produce < 30% of electricity by end of decade

AG "blah blah blah"

Unsubsidized, $6000 for a 3000 kwh/year system. That is $2/watt. This is not every install, it is for installation in my locale with a home that uses about 3000 kwh a year of hot water. I have the quote.

This should not be hard to understand, but AG is still denying AGW so he apparently thinks he has to be in denial about solar DHW, too.

 

I notice the "one PV to rule them all" posts get longer and longer, trying to paper over the basic facts, despite numerous posts to the contrary with real world examples, despite DOE. I think he must have bitten by a solar hot water heater as a child.

 

Can you tell me, from that doe document that I provided, how much solar saves versus heat pump? It says it uses more energy. DOE, the source you love, says you are full of crap.

We had one example from iccy, where he did not compare them. I certainly am not against DIY systems that do a litle of the work to another efficient system, but they do not scale. They make sense in handfulls of situation, while PV makes sense in millions of situations.

Solar water heaters were one of those ideas like the synfuels corp that was going to replace our gasoline with coal. Today the ideas have been superseded, and do not make much sense. You are proposing we all go to walkmans and crush our ipods. That beta is better than blue ray. None of it makes any sense at all.

 

They're just solar hot water heaters, Mr. Tweedy.

Solar hot water heaters are what they are, the least expensive, most efficient, most cost effective way to use solar energy to reduce one's home energy usage.

Don't see anyone saying solar hot water heaters were going to replace our gasoline with coal. That kind of wild and crazy analogy sounds like something from the Steve Martin/John Belushi Saturday Night Live routine where they try to top one another in meaningless analogies.

 

I never saw those routines, are they on youtube? The policies that first put forth solar water heater subsidies were part of the package with syn fuels, we still have both.

Solar water heaters are not cost effective for most of the country, solar pv is cost effective for a much higher proportion of home owners. Since you can not do math, you don't know this. You also don't seem to be able to be able to read that DOE comparitive report about solar water heaters being less efficient than heat pump water heaters.

 

Thanks for you opinion but I think we'll stick with the DOE analysis, conclusion and recommendation. Also Icarus and SageBrush messages above about real world installs are in line with the DOE analysis, conclusions and recommendations.

 

My problem with your misreprenting the DOE is not that solar can't supply 50% of heat, of an inefficient system, it just doesn't do that well with efficient systems.

We have the DOE doc above that says solar has a 9 year payback, heat pump water heaters have a 3 year payback and the heat pump water heater is more efficient. The DOE specifically points out high initial costs and potentially higher maintenance costs as disadvantages. The big advantage they point out is you can show your neighbors that you believe in solar, which seems me could be better done by choosing PV. The 9 year payback versus a traditional system does not include the higher maintenance costs.

Icarus, talked about the ineffeint water heaters, he did not compare his system to heat pump. The first thing when installing PV is first make the electric components more efficient, this has the fastest payback. Certainly you can improve uppon the efficiency of a heat pump by adding passive solar, but you can't get its net energy use to zero. For that you need PV. As I said I ignore Sagebrush, and if there is actually a real comparison post the numbers. You are quite lazy in not doing math, you are emotional, and you are sticking to the wrong conclusion.

Icarus did a fine DIY project, but it won't scale in the US. In Isreal where over 80% have solar hot water and the climate is suitable in most of the country, they think it has dropped energy use 3%. The US could not get close to that, and would spend much more money. Germany which is promoting solar PV and is worse for PV than most of the US, just anounced it got 4.5% of its power. I would love to get 25% of the US power from solar, and hot water heaters just aren't going to do it, even if they were $200 like in china. I like projects like Icarus did, they just won't get us very far. The more expensive antifreeze type systems have a much worse payback, often 50 years before subsidies, and the systems will need to be replaced long before that.

 

All this bickering goes away once a specific scenario is presented and the math performed. There are scenarios that can be encountered (or fabricated) that support any conjecture. Likewise there are many scenarios that change if any of the starting conditions are changed. That's one real disadvantage of engineering, there is really no room for emotion.

 

It is site specific but when talking that basic starting point, the DOE analysis provides a reliable fact based starting point.

​

You haven't had to mediate between two wildly emotional engineers each insisting his solution is the best.​

 

As a 54 year old EE, I beg to differ.

 

You've lead a sheltered life. The engineers get the most emotionally attached to their solutions.

 

I earlier wrote than solar DHW is $2/watt installed, but that is an error.

A lifetime $/kwh works out this way:
20-30 year life
3000 kwh/year collection
$6000 installation
20 watt pump operating 5 hours a day = 36 kwh electric used a year
Net annual kwh savings = 3000 - 36 = 2964 kwh

Lifetime kwh savings: 59280 - 88920 kwh
Lifetime energy cost = $6000/59280 = 10.12 cents a kwh down to 6.75 cents a kwh.
Unreported are pump replacements -- perhaps another $500 - $750 over the system's lifetime

These are unsubsidized costs.

--------
PV + HPHWH
PV:
$5 for 1.5 - 2.0 kwh/year*watt installed
-- 25 year lifetime, so 13.3 - 10 cents a kwh, or
First conclusion: PV with an old heater is more expensive than solar DWH.
If HPHWW cuts electric demand to 40-66.6%, then PV of 0.6 - 1.2 kw array needed.
-- At installed cost of $5 - 6$/watt, this is $3000 - $7,200 for the PV
Unreported are possible inverter replacement costs -- about $1/watt installed

HPHWH:
COP 1.5 - 2.5
10 years lifetime ? 15 years ??
$250 installation
$1500 tank
11 cents a kwh current national electric retail average
25 years of electricity will cost $5500 - $3300
Two installations will cost $3500

Adding the two together, PV + HPHWH for 25 years of equivalent heating to DHW costs (3k to 7.2k)+(3.5k)+(3.3k to 5.5k) = as low as $9,800, or as much as $16,200.


Conclusion: reports of solar DWH death are premature. Just be sure the locale is good, consumption matches production for most of the year, and a competent installer is involved.

 

Since you know more about my life than me, I have to bow out.

 

OK, I've written this post 3 times and it kept getting dropped becuase the new priuschat doesn't like me posting lowes URLs apparently

HPHWH:
$250 installation
$1500 tank

I wonder about these numbers

lowes.com shows it at $999 but some got it as low as $599 on sale. I know it's been as much as $1200 recently but I wonder how many have paid that much.

As to instillation that depends on if you have gas or electric water heater to begin with. My house had an old electric water heater so putting one in for me was simple. I can't imagine paying someone that much to install an electric water heater.

As to why I don't use gas heat or gas water heater we have:

My minimum bill is skewed by the "meter reading/billing fee", it is something like $12 or $13 before taxes so my minium bill with no heat or water used might be about $15.

I live far enough south I only turn on the heat about 3 or 4 months a year. That skews my heating bill by making me pay a minumum gas bill for 9-10 months on top of the gas used for heating.

I try to minimize my usage of hot water so if I'm not using gas heat I'm still paying a heavy penalty on the gas usage for the water heater. I'm assuming the electric water heater is more cost effecient than using a gas water heater once that billing policy is factored in.

To add to the fun I am using my heat pump water heater in a garage in a two story house. The garage is unconditioned but is below the master bedroom and two other bedrooms and the garage contains the air handler and ductwork for half the house. The cooling effect of the heat pump on top of the water heater is reducing the load for the heat pump that does the conditioned space so it is win/win.

The end result is that I have an eletric stove/oven, electric water heater, electric heat pump for cooling and heating. I beleive the net is equal to or better than what I would have if I were to try and add natural gas back into the mix and I don't have the added cost of the new gas furnace or the added complexity of a seperate bill for gas vs electric.

I'm assuming it would make adding solar PV more straight forward too as I'm all electric so I have a clear single bill to figure out my energy usage. I know the PV will be applied directly to my heating/cooling with no transmition losses or billing games by the utility company.

 

Note, I had this under ignored content, but since some think the numbers make sense I will respond.

Unless you are willing to put up with cold water, you will have a back up element. The question is not how much the unit says it saves, but how much it consumes. Here YMMV but Energy Star says most electric units have an ef of 1.8-2.0. This depends on the sun and your water usage.

A heat pump water pump normally has an ef of 2.2-2.5, which means it will use less electricity than that solar water heater, no matter how much the solar saves. YMMV and depending on conditions it may use more. That is the mistake here, back up heating of the solar hot water heater was ignorred. Your price of $9800-$16200 would be for the HP hot water to be supplied by solar completely, while that solar water heater would still need electricity.

Because of incentives, the solar comes out better than this, and these should be used for cost comparisons. From your numbers though
Solar $6000
Heat Pump $1750
With the heat pump in most cases using less electricity. The solar will need higher maintenance but has a longer usefull life. PV should have a longer usefull life than the solar. If in your individual cercumstances the heat pump is less efficient it will only be slightly less efficient, and the PV comes into play. In New Mexico PV should add value to the home, I doubt that solar hot water heaters do. In most cases the decision to add PV is a different one, but if you want solar, and to improve energy on hot water, these decisions can be coupled. Certainly insolation, energy efficient washer/drier and dish washer may have faster payback.

 

One of the primary things is my design for interior storm windows. see: Green Fret Consulting - Interior Storm Window

For most people around here who are in need of fuel assistance, these have a payback of less than a year. In other words, they are cheaper than giving the person an equivalent amount of fuel, and then you get to use them again next year. There are a number of non-profits that are making them, including the local Habitat for Humanity, as well as the non-profit I am involved with the Midcoast Green Collaborative. Midcoast Green Collaborative - home page

 

You were the one who said you had never been in a situation where engineers get emotionally attached to their solution to a problem. I have had to mediate a fair number of engineer vs. engineer discussions where each had his own solution and were emotionally attached to it. This discussion is actually typical. It is when one side can't see the possibilities of both solutions having value in different situations that you can see the emotional attachment is clouding a person's judgement. In this case you have a person who insists photovoltaic solar panels are the ONLY solution despite the large body of evidence from unbiased sources like DOE that solar hot water is very effective in many cases with the DOE stating solar hot water will be cost effective in the large majority of cases.

 

I said nothing of the sort. Reread to see what I actually said, which is quite the opposite.

And I will continue to stand by what I said. Regardless of what any person or organization's position, given the scenario, conditions, cost and goal, the final calculations and cost will reveal the optimum solution. It may not be what someone wanted or expected, but that is engineering, not politics. No amount of emotional attachment changes the math.

 

I am not going to argue about all of this. bottom line, is it is not always bout the money, Certianly not in today's dollars. for example, if I had Nat gas, would I junk the solar and burn "cheap" Nat gas ? Would I convert e propane to Nat gas? Of course!

Getting caught up with cost is A. It short sighted. My simple DIY system has been working for nearly 30 year, with out a single replacement part. (I did install a diffent controller because the new one has the anti freeze cycle). Bottom line, unless (and note I did say if, AND I noted it in my earlier post) you've in an A/C environment, solar hot water clearly the referred option if yard looking for sustainability. I take your point about the relative efficiency of PV vs hot water, what you have to compare useful "work done" in the net,, in the end how many BTUs can you get into how much water at wht cost.

For a simple comparison, let's assume you use 100 gallons of hot water a day, at 70f rise. 100*8.34*70=58,380 BTUs.

58,380 BTUs is About 17 kwh worth of power. A 5 kw PV array in central South Dakota for an example, might cost ~$20-25,000, and would put out an average daily output (according to PVWatts ~33kwh. So it would take roughly 1/2 of that PV capacity simply to heat the water. So, the simple question is how much would it cost to install a solar hot water system for the same 100 gpd?

I would be hard pressed to think it would be $10-12k. Drop the price of PV another factor of 10 and we will look at the equations again.

Icarus

(I. Have no real idea of the installed cost of hot water recently, but someone tried to sell me a evacuated tube system recently as a DIY for $2500 new)