Tepeo Zero Emission Boiler

[MJNewton]

I searched before posting this and found a couple of threads on this product, but the latest was from back in 2019 which seems like a lifetime ago in terms of where the energy market has gone since...

 

The 'ZEB' seems to be an electrically-powered thermal heat store which purports to store up to 40kWh of energy with cost savings promised by using low cost off-peak (or, more specifically, time-of-use) charging. It claims high compatibility with existing housing stock that might not be well suited to fully benefit from heat pumps that ideally require better insulation and larger radiators etc, and I am wondering if behind the inevitable marketing shine there might indeed be some merits with it?

 

There's a video here which covers some aspects, albeit in not all that much detail, but it is presented by Kryten which I think is how it ended up in my Youtube feed!

 

 

 

Does anyone know much about them? Like all things there will be pros and cons, but there are a few things about it that have intrigued me. Our gas boiler is 15 years old and so is sure to be on a countdown timer to eventual retirement and I've been thinking about what I might replace it with and an ASHP isn't looking too attractive given the small radiators and 10mm piping we've got here, and with the gas-electricity price differential now narrowing (factoring in off-peak electricity at least) I am wondering if something like the ZEB may turn out to be a possible candidate when the time comes? With it being such a simple single-box approach it looks like it could potentially be a DIY install too which greatly appeals to me, as does the presumably low maintenance overhead too?

 

Would be grateful for anyone's thoughts!

Edited November 15, 2022 by MJNewton

[ProDave]

I have never been convinced about "electric boilers"  I am still waiting for someone to tell me what an electric boiler brings to the party compared to individual electric panel heaters in each room?  Apart from looking like proper central heating with wet radiators.

 

 

[JohnMo]

Think of a storage heater, but with an air to water heat exchanger instead of and air to air exchange.  Idea is pretty simple, would suspect its very heavy, filled with bricks similar to a storage heater.  So its really a high density thermal store.  Key advantage over water is installed space required is way less.

 

40kWh sounds great, BUT, if you take away 5kWh for DHW it only leaves 35kWh hours for heating (1.45kW per hour based on 24h) and also depends on the threshold of where in the 40kWh the heat becomes unusable from the store, due the heat exchanger performance and the delta T required.  Also if a top up is required during the day - not cheap.

 

According to the manual it looses 15-20% of its charge over 24hrs, which is huge. So 6-8 kWh, which is the equivently of about 3-4 300L cylinders.  But 2x300L cylinders would hold about the same energy at 60 degs, with half the heat losses.  So if you had space would be better and possibly cheaper run on the same E7 tariff or similar.  Also when its cold outside you could charge to higher temperature (to store more energy), in the summer just charge one cylinder for DHW to save money.

 

Something borrowed from another website, the Octopus refers to a heat pump run on the night time tariff.

 

 

[MJNewton]

2 minutes ago, JohnMo said:

Idea is pretty simple, would suspect its very heavy, filled with bricks similar to a storage heater. 

 

300kg or thereabouts I think I read/heard!

 

Quote

40kWh sounds great, BUT, if you take away 5kWh for DHW it only leaves 35kWh hours for heating (1.45kW per hour based on 24h) and also depends on the threshold of where in the 40kWh the heat becomes unusable from the store, due the heat exchanger performance and the delta T required.  Also if a top up is required during the day - not cheap.

 

That's a really good point, and having now looking at my previous peak-winter heating demands I see we can going through 50-70kWh/day (sometimes briefly higher) so it would certainly need day/realtime topups which would of course undermine the timeshifting benefits realised through its storage ability.

 

Perhaps not so viable an option for me, and hopefully if we can get a few more years out of the current gas boiler it might become more obvious what its replacement should look like. My main concern is that I don't think we could make our radiators bigger without severely ruining the aesthetics, and not to mention the 10mm plumbing that serves the majority of radiators too, and so I am hoping that ASHPs continue to evolve such this might not remain an issue.

[ProDave]

10 minutes ago, JohnMo said:

40kWh sounds great, BUT, if you take away 5kWh for DHW it only leaves 35kWh hours for heating (1.45kW per hour based on 24h) and also depends on the threshold of where in the 40kWh the heat becomes unusable from the store, due the heat exchanger performance and the delta T required.  Also if a top up is required during the day - not cheap.

1.45Kw average heat output would not be enough for my low energy house for the coldest periods in winter, so how this is expected to work for an ordinary house beats me.

 

A large individual storage heater is usually sized at 21kWh storage (3 kW input for 7 hours) so this box is essentially 2 of those.  If it is using the same storage bricks then that is going to be a massive weight to hang on a wall.

 

This is not a new idea, look up the Electricaire which was still available or if not was still available recently.  They were fitted into a lot of houses around here, they are a massive central storage heater and the heat is distributed on demand by air by turning on a big fan to blow air through the core and then to the rooms.

 

You can get larger capacity storage boilers based on a large water tank typically with 9kW of heat input.  They can work reasonably well, particularly if used on E10 rather than E7 as you get more cheap rate and split into 3 chunks one all on one go.  But nothing is going to change the fact that off peak is only half the cost of peak electricity (with the penalty that peak rate is higher than a single rate tariff) so is never going to match the cost benefit of a heat pump.