Summer Solar diversion to a Sunamp battery

I’ve just had 4kw of solar panels installed to link to a GE 9.5 kWh battery and 3.6kwh inverter. Even in March it’s obvious that there is excess energy in the afternoons with at least 4kwh spare. We are on oil fired space heating and DHW but plan to do way with the hot water cylinder and use electric from solar and from offpeak grid when the solar excess falls off to heat all our DHW.

I’ve bought a Sunamp Uniq 9 ( 210 litre equiv) phase change heat battery for a very modest price £500. It can store 10kwh nd is charged with an internal immersion element rated at 2.8kw. So thinking of using a GE Smart plug , £13!!! And the App to switch the Sunamp on for 100mins each day from May to Sept.
Why should I buy an EDDI or an IBoost at £400? Am I missing something ?
Bill G

Certainly the Eddi has many more features that a smart plug.

More to suit someone without a battery, it can automatically modulate the diverted power based on the excess (minus an export margin of say 100 W), so avoiding any grid import when the generated excess is less than the full rating of the immersion element.

Also it can automatically switch between 2 separate outputs when the 1st output reaches the target temperature.

I have output 1 wired to the hot water tank immersion, and output 2 wired to 2 oil-filled radiators for Winter use.
Also with an add-on relay PCB, it has the facility for extra logic control and 2 x temperature sensors with logging of data.

Comparing a smart plug with the Eddi is not like for like, but since you have a battery a smart plug may be all you need.
All assuming the switching contacts in the smart plug are up to the job of regular on/off operation of the 2.8-3.0 kW immersion element.

Simon_C

Thanks for that Simon , I’ll drop Givenergy an email to see the their plus are good for that.

The Sunamp will cut out at least 800 litres of oil usage a year!!!! Our old cylinder had no facility for immersion and is very lossy in heat terms . Sunamp is 4 times better at heat retention and has a vacuum casing. I reckon it will only need 4kwh a day recharge but we’ll see. Digging out the old vented direct tank also connected to the oil boiler and a back boiler coal fire is going to be the challenge not fitting a new Smart plug.

BillG

billG I’ve bought a Sunamp Uniq 9 ( 210 litre equiv) phase change heat battery for a very modest price £500.

That's a really good price. List price is a lot higher. Where did you manage to get it for that price?

An alternative for controlling it is to use a powerful dimmer in the circuit to lower the wattage. Something like this.

billG Maybe just check the calcs? With 4kWh spare (by my calcs), it'll raise the temperature of 210l of water by about 16℃. That might be all you need and if the heater is just heating the top half, it'll be 32℃.

Tim That’s not how a Sunamp works it only contains about2 litres of water! It’s an on demand water heater. Cold water in hot water out at mains pressure. There are other variants than also be charged via heat pump or oil/ gas boiler. The energy is stored ina phase change material very similar to hand warmers. Possibly 100 litres? But it can hold 4 times the latent heat of water and gives up its stored heat when old water is passed through an internal heat exchanger. It’s a world beating Scottish invention made locally.so far 30,000 made.
Good for 50,000 heat cycles. My size would have been £2800 new but I’ve bought a 4 year old one for£550. You can get bigger or smaller ones. Other folk are telling me a recharge of 4kwh of offpeak electricity ( 60p total😊) does a days DHW, in summer the recharge from solar is free. .Google Sunamp. Bill G

Woodlands Second hand on EBay the guy. Had at least half a dozen from an office refurb. I did see new ones , same size for £1350 but I was too slow to bid . Bill G
Ps will need to test it before I fit it though!

billG The energy is stored ina phase change material very similar to hand warmers

Perfect. Looks like, depending on how much water you want to draw, it’d be a very useful way to store energy.

Tim My main initially aim was to cut out using expensive oil in Summer just to heat water in an oil fired hot water cylinder. It’s been taking 3 litres of oil a day , that’s£2 min , sometimes £3 a day depending on the oil price. But even in Winter there are considerable savings ,So cutting out 365 days of oil ( for DHW ) at those prices adds up. It should pay for itself in one year! 😊In summer my hot water will now befree and in winter by using off peak at 15 p a unit, a 4kwh recharge will cost 60p . A no brainer!

Bill g

billG off peak at 15 p a unit

which tariff is that?

positor1 We are with Scottish Power daytime units are 47.9 p offpeak white meter rate 15p standing daily charge 61p

If I could be bothered getting a smart meter? My excess generation could be sold as SEG at 12p a unit (all new rates they introduced about a month ago)

The 10 kWh Sunamp is now fully installed and the old hot water tank and cold water tank removed and all my plumbing much improved to suit the Sunamp. Two Solid days work by an amazing heating engineer, who also installed a new shower and decommissioned our back boiler.

The 10kwh Sunamp managed to produce 8 showers and 3 or 4 washings up before I’d drained the heat from it deliberately. We had 4 folk in the house over two days. Now back to normal so going to set a timer to put two hours each afternoon ( at 2.8kw rate) to start with, possibly will need less. This to be the summer strategy. The Sunamp will take this power from the fully solar charged ( normally by 1pm) GE 9.5 battery & the solar panels .(We aim not to use ANY daytime grid units) Our normal daily house demand is about 5kwh The Sunamp has little or no controls, other than on:off from the timer. The Sunamp LED indicators seem to a have life of their own so hopefully it will settle down( It was 2nd hand at 1/5 the price of a new one 😊) it switches off when fully charged.
So free hot water for the summer as well as free electricity. Any top ups for sunless days for both batteries can be offpeak at 15p/ unit. Our panels can generate between12 and 22 kWh each day so still giving some energy to the grid for free…

The next fortnight looks very sunny so ideal testing conditions. , Bill G

Coming up for a year since the 9.5GE battery and 4kw of solar panels were installed. Has run faultlessly for a year since it was installed. Charging period adjusted for the seasons. Now will look into how to get paid for excess energy production as we get into the sunnier months . I now have a smart meter and export MPAN number so shouldn’t be too painful? The Sunamp heat battery installed last June takes about 4 kWh per night but will soon be able to be charged from solar. The house itself needs about 6kwh. About to insulate the internal walls of this Victorian cottage with a 75% grant from Govt/EST . So next winter season also hope to cut my oil usage even more? And a little less electricity as the boiler shouldn’t run as much?

billG Hi Bill Please let me know if you hear back from GivEnergy on whether they think their smart plugs will cope with regular 3kW usage. I've just had an electrician replace my backup immersion heater switch with a plug and a socket (so I could use a smart plug). He said he thought their 16kW capacity would be sufficient, but I've yet to try it.

Niceguy
A lot of smart plugs are made with cheap components - see the recent post https://community.givenergy.cloud/d/4047-givenergy-smart-plug-nearly-burned-down-my-house

The GivEnergy plus are only rated to 10A continuous.

The mylocalbytes smart plugs are rated to 16A.

Personally I would be careful running an immersion heater with a smart plug. There’s dedicated proper relays for this

Niceguy I am very surprised that an electrician did this. Regardless of the smart switch, 13A plugs and sockets are not rated for 16A. It's just spring clips holding the fuse in the fuse holder, and gripping the pins in the socket. And using plug-in smart switch means two sets of pins to go through.

Probably better to use the smart switch to control a wired-in relay or contactor, so that the power through the smart switch itself is minimal.