Electric thermal storage unit

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Azzura

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#191067 22-Jan-2016 09:09

Not sure if these units are already in NZ or if they will ever get here (I am sure they would eventually).

I only came across these ETS units via reading a new story from Canada. Apparently they are popular in Europe.

Just thought some might be interested in knowing about these units and perhaps offer some alternative to winter heating woes.

timmmay

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#1476559 22-Jan-2016 09:13

It's like the old night store heaters. Makes sense, it's easier to store heat than power.

Spirax

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#1476568 22-Jan-2016 09:20

Uh, these have been around for years. They used to be called Night Store Heaters and I have two in my house. A 2.5Kw unit in the hall upstairs and a 1.8Kw unit in my wife's workroom downstairs. They use off peak power (11pm - 7am) at a reduce cost. Excellent to take the chill off a cold winters morning.

wellygary

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#1476613 22-Jan-2016 10:08

As Above, have been around in NZ "since ages ago" and are still avaiiable, just under a different name...

http://www.devi.co.nz/wp-content/uploads/2015/01/Marketing-brochure-technotherm-night-store-heaters.pdf

Azzura

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#1476628 22-Jan-2016 10:35

Ahh cool. I had done a quick search but nothing came up immediately and I hadn't caught any mention of these kind of units on the forums.

Aredwood

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#1476990 22-Jan-2016 17:56

Better off just using a large hot water cylinder as thermal storage.

raytaylor

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#1477980 25-Jan-2016 00:18

Still cheaper to use a heat pump

The offpeak rate is around 50% of your onpeak rate (based on energy online's pricing).

A heat pump will typically give you 4x efficiency in addition to off peak savings, but the night store cant give you any more than the 50% efficiency by taking advantage of the off peak price drop.

Lets say you wanted to produce 10 kwh of heat. 4kwh is to be released during the offpeak hours with the rest released in the morning during on-peak. On peak rate is 25c per kwh. Off peak rate is 12.5c per kwh.

The night store heater could directly convert 10kwh of electricity into 10kwh of heat during the off peak hours. then release that heat slowly into your on-peak hours. Total cost $1.25

The heat pump could directly convert 1kw of electricity into 4kw of heat during the offpeak hours, and then 1.5kwh of electricity into 6kwh of heat during the on-peak hours. Releasing as it converts the energy. Total cost $0.63

Now if you use a few hot water cylinders to store the heat, its much better thermally insulated meaning the heat will last in the storage container for much longer. Days in fact.

You can then heat that water with a heat-pump water heater and distribute it into the home with a radiator. This can allow you to produce all heat with a heat pump during the offpeak hours, The heat pump water systems advertising material shows they are closer to 3x efficient but thats mostly due to the higher temperature difference they need to work with. So if we use their figure of 3x efficiency, it brings the daily production cost down to $0.42

source- fujitsu and rheem

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timmmay

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#1477998 25-Jan-2016 06:31

@raytaylor with Flick Electric it can be more like 3X, and a heat pump in non-ideal conditions may only get to 3X efficiency. Though in general I agree with you. You have to take into account that a heat pump or heat pump water heater is a lot more expensive than a night store heater too.

raytaylor

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#1478063 25-Jan-2016 09:53

timmmay:

You have to take into account that a heat pump or heat pump water heater is a lot more expensive than a night store heater too.

This is very true

Ray Taylor

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richms

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#1478131 25-Jan-2016 11:48

Also the heatpump will have a shorter life than a basic heater in a box full of rocks type heater.

Richard rich.ms

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#1478158 25-Jan-2016 12:13

What you need is a heat pump that runs at night and heats those bricks, so you pay 1/3 for power and get 300% efficiency, for a 900% gain over a regular heater, at the cost of high purchase price and complexity.

richms

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#1478248 25-Jan-2016 13:45

Dont the bricks get up to several 100 degrees tho? Outside of what a hearpump could achieve?

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timmmay

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#1478278 25-Jan-2016 14:12

richms:

Dont the bricks get up to several 100 degrees tho? Outside of what a hearpump could achieve?

Probably, now that you mention it.