Electric Backup

peakbagger · Mar 7, 2012

I did some quick back of the envelope numbers and discovered that in the PSNH territory of NH (most of the state), at around $3.64 per gallon of #2 oil, the off peak electric thermal storage rate costs are just about the same per million btu as heatrng oil. I used an 85% efficiency for the oil and 100 % for electric.

Heating Oil 138000 btu/hr
Cost $3.64 $/gal
Cost per MMbtu $26.40 $/Mmbtu
boiler efficency 0.85 %
Cost per btu to storage $31.06
Off peak rate 10.6 Cents/kw

KW to BTU 3413 btu/kw
Efficiency 100 %
cost per BTU $31.06 $/btu

I guess I need to start looking around for a deal on an imersion heater

Since I already have the oil tank and furnace, it doesnt make sense for me unless the heating oil goes up substantially, but for those planning storage who dont have an existing oil furnace or only have one flue in their chimney, this might be a good option as it allows them to buy a wood boiler and spend the money on the storage tank instead of on a furnace.

hobbyheater · Mar 7, 2012

Switched to electric backup from oil for a different reason. The oil backup got very little use and the furnace oil quality became an issue, making the oil boiler unreliable.

heaterman · Mar 7, 2012

peakbagger said:
I did some quick back of the envelope numbers and discovered that in the PSNH territory of NH (most of the state), at around $3.64 per gallon of #2 oil, the off peak electric thermal storage rate costs are just about the same per million btu as heatrng oil. I used an 85% efficiency for the oil and 100 % for electric.

Heating Oil 138000 btu/hr
Cost $3.64 $/gal
Cost per MMbtu $26.40 $/Mmbtu
boiler efficency 0.85 %
Cost per btu to storage $31.06
Off peak rate 10.6 Cents/kw

KW to BTU 3413 btu/kw
Efficiency 100 %
cost per BTU $31.06 $/btu

I guess I need to start looking around for a deal on an imersion heater Since I already have the oil tank and furnace, it doesnt make sense for me unless the heating oil goes up substantially, but for those planning storage who dont have an existing oil furnace or only have one flue in their chimney, this might be a good option as it allows them to buy a wood boiler and spend the money on the storage tank instead of on a furnace.

You are on the track of something that Garn is addressing right now. Being that they understand the concept of heat storage and what it can do, they are developing a stand alone unit that will sit on a pad in your back yard just like an OWB. They have some out undergoing field testing....yes actual out in the real world testing.....as we speak. So far it is performing flawlessly and they are looking at production within the next year or so. As I understand it the off peak unit will come as a pre insulated package ready to set in place and complete with heating elements and controller. It will be piped into the house just like any other outdoor unit.

I am aware of a few Garns out west that were sold with their electric element kit and are being used in that manner. They have never had a wood fire in them. The cost on the off peak storage unit will be far less than a wood burning Garn. Might be something to consider.

In many areas the utilities have rebate programs for offsetting the cost of this type of equipment so you might want to check into that in your area and see what's up.

peakbagger · Mar 7, 2012

The former governor of Maine (now senate candidate) was pushing an off peak heating rate to peddle excess wind power when it wasnt in demand. I dont think it went anywhere.

I know of at least one older system in the area that has a heating coil in their storage tank on on peak rates

I did a quick look and Omega Engineering has an over the side heater (needed for my storage design) for $1,000. Omega is convenient but expensive. If someone has pressurized storage and is planned to weld on it anyhow to add fittings, it wouldnt take much to add a coupling for a standard imersion heater.

Medman · Mar 7, 2012

This is very timely because I was just kicking this idea around in my head. For my setup with forced air heat and DHW sidearm the lowest useable temp I can pull from storage (depending on outdoor temp) is about 140*. I was thinking of installing an immersion heater in my storage tank and using the PLC control to turn it on as a backup during off peak hours. Using the above numbers, it would cost about $6 to raise the tank temp to 190* with no demand. I think this is a reasonable number, considering the very few days I would need the backup each year.

Thanks for the info. I'm still doing the design for storage and control, but I have the PLC program and temp sensors up and running. Adding a few ladder lines for electric backup control will be easy.
Any ideas on what type of immersion heater hardware I should be looking at?

Ryan

peakbagger · Mar 7, 2012

The numbers will change depending on your rate structure which may be far different in Canada than NH. So first thing is to read you rate sheet and see if you have a off peak storage rate and plug them into my calculations. In NH I would have to install a seperate meter and pay $10 a month for the extra billing paperwork. I have solar electric so I would be selling them power back at full rate when its sunny during the day and buying it back at night when its cheap.

I havent done any research but somehting like this http://www.omega.com/ppt/pptsc.asp?ref=ARMT2_HEATER&Nav=heaf01 would work as long as you have the right fitting on your tank. I have a rubber liner so I can not use this type. I expect someone could save some money by just getting an element for an electric hot water heater and adpating the tank to fit it. I saw one of these on line for $10, so its worth getting creative.

Medman · Mar 7, 2012

We already have smart meters (at a cost of $1.3 BILLION for Ontario alone!) with an off-peak winter rate from 7pm to 7am. I have already put a timer on my DHW tank limiting heat to off-peak time (when the boiler is not running, of course). The rates are about half of peak during off-peak times, and there is a mid-peak period during the mid-day in winter.

I wonder if a DHW element would be a little undersized for this application. Running full-out it still might not be enough to heat 500 gallons quickly enough to satisfy demand. I would think there must be a commercial option - like the elements the Garns use perhaps? Could I buy one from Garn? What is the cost?

maple1 · Mar 7, 2012

I was thinking about this in the fall also:

https://www.hearth.com/econtent/index.php/forums/viewthread/84577/

I'm still leaning to staying with oil for back up, although I'll need a new boiler and likely tank also in a couple years.

My last bill was at 0.16/kwh, bottom line. I have since found out we have off-peak rates here in Nova Scotia, but you have to have a qualified electric heating system (e.g. one that stores heat at night time - ETS?) to get the good rates. That makes no sense, if they're serious about it they should just let anyone who wants to take advantage of night time rates to buy a new meter and do it. Things are a bit backwards up here at times...

dpsfireman · Mar 7, 2012

I used a hot water off peak electric system for 15 years until the electric company pulled the special rate and it was awesome. No maintenance, the only problem I ever had was a small leak in a zone valve which was fixed by tightening the bolts on it. If they didn't do away with the rate I would not have looked for an alternative, the Biomass I have now.

jebatty · Mar 8, 2012

This may be very backward thinking, except literally only for backup, but, at least for us, certainly never for primary heating to replace wood, such as an "electric-fired" garn-type unit, as described by heaterman, if I understand his description correctly, or other electric heating storage appliance which can take advantage of off-peak rates.

From our electric co-op in MN we have both off-peak, current rate $0.043/kwh, and dual heat (interruptible), current rate $0.053/kwh. Our house has electric baseboard, 35,000 btuh equivalent, which adequately heats our house, if we used it. We burn wood, however, and average volume of wood used for the house is 4-5 cords per winter of aspen, which at 14.7 million btu/cord = 4,308 kwh/cord x 4.5 cords = 19,386 kwh x $0.043 = $833 of electricity equivalent, if we heated with electricity, and if we were on the off-peak rate, the lowest available.

A cord of aspen in our area, bought in a 10 cord truckload volume, is currently about $75/cord x 4.5 = $338.00, less than 1/2 the electric cost equivalent. It would make no cent$ to use electric, and we don't use electric -- in fact, we ran from it as fast as possible during the early part of our first winter in our house in 1990, and promptly bought the wood stove then, the same stove we use today. And in the future we may make the change-over to wood gasifier boiler and install low-temp radiant in the house. I already use a Tarm for my shop in-floor radiant, and the ease of heating with the Tarm and pressurized storage is dramatic. I would make the change now, except my wife loves the wood stove, the warmth it bring along with a fresh brewed cup of coffee in the morning, sipping quietly while sitting in the easy chair in front of the stove.

In our case the wood also comes from our own land, so we don't even have the purchase cost of the wood, which makes the electric even more backward and costly.

At least in our area, electricity is certain to go up in price, impacted by and fueled by world energy markets. Knowledgeable people around here predict a price doubling in 10 years. Wood is local, readily and widely abundant, available and sustainable ("free" in fact from our own land). I would be very cautious about investing in a fossil fuel dependent heating source when wood is readily available.

And finally, if a person purchases wood from local firewood cutters or loggers, those purchase $$$ are supporting the local economy, providing local jobs, supporting local families. Wood also is carbon neutral. The bulk of the $$$ to purchase electricity generally are shipped to the oil/gas or coal supplier, far distant from local economic support, and their use also contributes to mercury and other pollution, as well as fossil fuel CO2 in the atmosphere and other environmental degradation.

This is not to say that in some areas where costs are much different than where I live electric-storage heat is not economical, but it comes with other costs and detrimental impacts from which wood is largely free.

heaterman · Mar 8, 2012

Around here (Michigan) there are no off peak rates except for a couple very small Co-op's near the tip of the mitt. I don't see an electric storage unit as replacing wood fired equipment at all but I think there may be a market for it in areas where off peak is very cheap (<$.04/KWH) or in areas where wood burning may not be appropriate. A person in the middle of a city suburb could take advantage of an off peak storage unit whereas a wood burner may not even be allowed. As with all things, it wouldn't be for everyone.

woodsmaster · Mar 8, 2012

Wow Jabatty you have cheap power to. I pay almost .13/KWH after fees and tax. .0985/KWH before fees. They even give me a small break for having an elec. water heater, Hopfully they don't figure out I'm not using it. I use about 8 cord a year so that would be a huge sum for me to heat with elec.

peakbagger · Mar 8, 2012

The rational for offpeak backup is that there is labor involved with wood that isnt required for electric. If I am home and able to move, shame on me for not using wood. But if I am gone for more than a couple of days (or weeks) in cold conditions, I need a reliable backup that doesnt require labor. To date I havent seen a viable options for burning wood over a long period unattended. For those who need a mortgage or to potentially sell a house, the bank also requires an unattended backup. If someone is building a new place or setting up a new system, it makes sense to me to minimize the cost for backup and it looks like off peak electric is the least initial cost that integrates well with a wood boiler. Sure high end pellet boilers can run unattended for weeks at a time, but the fuel cost is at a premium to local firewood and I expect pellets to rise significantly in the Northeast due to the current rush to supply Europe with pellets at far higher profits (definitely worth a entirely seperate discussion). Obvious if natural gas is availlable, the discussion changes significantly, but its not going to happen anytime soon for most of Northern New England.

As for element sizing, my storage is 550 gallons (8 lbs per gallon ) and I can run it up to 190 deg F and I run it down to 140F as I have standard baseboard, that is roughly 220,000 usable btus stored in the tank. That covers my house load for 24 hours in cold weather, so for full backup, I need to charge up the tank during off peak hours, usually 8Pm to 8 AM (12 hours). So 220,000 divided by 12 = 18333 btu/hr, now divide by 3413 btu/kw and that ends up as 5.37 KW of heater required. In reality I would use less heat as I would have the thermostats set lower while I was gone. An average hot water heater is 4.500 KW. I dont have the specs right at hand, but expect the two elements total 4500 watts so someone would need three hot water heater elements to supply the backup or they could easily buy a single heater with enough capacity (but at higher cost)

NH has a large nuclear power plant and a couple of coal plants that are baseloaded, it takes too long to ramp them up or ramp them down, so they run at full load. There are also a lot of run of the river hydros in the state with no storage so they run all the time and the power is close to worthless off peak as all the other regional utilities are in the same shape. By selling power off peak with the capabilities of remote switching of the heaters (required in NH), they get some value for power and if there is a sudden grid issue, they can shut off the of peak heaters for a few minutes while they bring on reserves. I expect off peak rates will be around for awhile in this market. I do expect that the price of on peak electric power will go up with the advent of smart meters. There are some areas of the country already with multiple tiered rates and if you want power when its in high demand you may be paying triple current costs to dissuade you from using it. In no way and I advocating real time electric backup as that is going cost a bundle.

jimbom · Mar 8, 2012

jebatty said:
...And finally, if a person purchases wood from local firewood cutters or loggers, those purchase $$$ are supporting the local economy, providing local jobs, supporting local families. Wood also is carbon neutral. The bulk of the $$$ to purchase electricity generally are shipped to the oil/gas or coal supplier, far distant from local economic support, and their use also contributes to mercury and other pollution, as well as fossil fuel CO2 in the atmosphere and other environmental degradation...

++++eleventyone

Medman · Mar 8, 2012

I think jebatty is right to say that the electric off-peak option is good for backup only, which is my application. Peak rates here are close to 15 cents/kWh, off-peak is about 7.5 cents. Being able to heat storage (like I do for DHW) during off-peak hours would be a good backup fot the 8-10 days a winter that no one is home to feed the boiler. Iagree that electricity is only going to increase in price in the future - we have already been warned of a 50% increase in the coming years to pay for "green" initiatives.

As for supporting local woodcutters, I have been having a very difficult time this year getting any local loggers to deliver logs. They are feeling the costs of higher fuel prices and most are now just chipping all the hardwoods and filling box trailers right in the bush. This hog-fuel is being used by local pulp operations as fuel for their boilers, to produce pulp and paper products. Its a real shame how much good oak and hard maple is being burned in this way. Many of the locals are not even working in the bush this winter because of the high fuel costs and low demand for hardwood sawlogs and pulp logs.
Its a real pickle, because many have switched to wood here and now the supply has dried up.

joecool85 · Mar 8, 2012

I know it keeps getting mentioned that electricity rates are going to go up, but here in Maine the best other option is oil and we KNOW those rates are going to go up, probably faster than the electric! I'm seriously considering switching to a wood boiler with storage and electric backup either via an electric boiler or in-tank elements.

heaterman · Mar 8, 2012

Here's a really good website that lets a person compare fuel cost per actual delivered million btu while factoring in efficiency . Get's pretty interesting when electric is at less than 6 cents/KWH. Of course regular electric rates of $.11-.13 / that most of us pay bring things right back in line with Oil and LP gas. Thankful I live in an area with natural.

www.eia.gov/neic/experts/heatcalc.xls

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Electric Backup

peakbagger

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hobbyheater

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heaterman

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peakbagger

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Medman

Feeling the Heat

peakbagger

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Medman

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maple1

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jebatty

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heaterman

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woodsmaster

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peakbagger

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jimbom

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Medman

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heaterman

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