We have customer trials which resulted in happy customers but precise analysis of the device in operation was though essential. The device has been validated and we are happy to report that it maintains stratification when charging and it demonstrates near perfect stratification on discharge to maximise the energy stored. The benefits are highlighted below as are the results of the validation.
Running Cost
Costing between 3p and 6p a day to run it can save over a £1 day, paying for itself in under a year (12 KW/Hr stored at 7.14p off peak compared with 26.61p daytime rate).
Installation Cost
Costing £250 , this device fits on top of an existing cylinder and it can be fitted in under 15 minutes by a competent DIYer. It turns any existing tank in a home into a heat store. For those having changed to a tank less plumbing system its well worth switching back. It enhances the efficiency of an existing immersion heater so there is no need to upgrade the length or buy a special heater.
Reduction in gas consumption
The device reduces gas consumption by 20% to 30% in a typical home with a gas boiler.
Grid stabilisation
The device uses no electricity during the day as it only stores surplus grid electricity at night. Night time electricity is typically 100% ‘green” as peak electricity generated using gas is only fed into the grid at peak demand
To validate and quantify potential energy storage a energy storage device has been fitted to a 210 litre hot water cylinder and we have been cycling the heat storage process to determine energy storage and retention. The energy storage for the device was commenced on the 7th May 2024.
A 210 litre cylinder is typical in a 2, 3, and 4 bedroom homes
The validation is for a 210 litre cylinder.
Typical Heat Retention & Stratification
Heat loss over time
TIME ELAPSED 0HRS 12HRS 24HRS (FALL IN 24 HRS) 36HRS
TOP OF CYLINDER 57.7 55.8 54.6 (3.1 DEG C) 53.0
TOP 1/3RD 57.9 56.0 54.6 (3.3 DEG C) 53.0
MIDDLE ** ** 54.3 (NA) 52.7
BOTTOM 1/3RD 56.8 55.0 53.5 (3.3 DEG C) 51.7
BASE 48.8 46.3 44.8 (4.0 DEG C) 42.2
Energy ‘lost’ over 24 hours = 210 x 4 x 3.2/3412 = 0.78 KW
Energy stored in hot water at night is normally used the next morning plus this calculation discounts the heated water used the next morning which no longer remains in the tank. The actual heat loss is closer to 50% of the above figure. In my own home I pay 7p per KW so the running cost would be between 3p and 6p a day.
Retention of Heat Stratification on demand (cold water enters bottom of tank and hot water leaves top of tank)
Demand Simulation commenced 7.02 am 9th of May 2024
TIME ELAPSED 0MINS 15MINS 20MINS 24MINS 35MINS 133MINS 173MINS
DEMAND SHUT OFF AT 35MINS
DEMAND CONTINUED AT 133 MINS
TOP OF CYLINDER 53.0 52.9 52.8 50.8 48.0 17.6
TOP 1/3RD 53.0 52.7 51.3 32.2 28.5 16.4
MIDDLE 52.7 49.9 34.4 21.4 17.5 15.8
BOTTOM 1/3RD 51.7 33.3 24.7 21.1 16.9 15.7
BASE 42.2 29.9 27.7 25.3 17.5 16.2
An impressive performance with the tank retaining statification throughout.
The temperature drop between 35MINS and 133MINS illustrates the delay in the copper tank cooling in reaction to lower internal water temperatures.
Hot water stored using an immersion heater only :-
TOP OF CYLINDER 67.0
TOP 1/3RD 48.5
MIDDLE 18.0
BOTTOM 1/3RD 15,6
BASE 16.1
The WRIGHTCHOICE ENERGY STORAGE
Whats in the box
Tank Device
Energy storage device with a 12 volt micro pump.
The devise is factory set so as to trickle feed hot water to the base of the tank as a rate below that heated by the immersion heater.
Variable voltage transformer (9 & 12 volts)
10mm dip pipe
Control Device
Top tank sensor.
The top tank sensor is an extra which is only required for customers wishing to store surplus self generated PV electricity.
The top tank sensor activates when the water in the top of the tank is above 60 degrees C.
Only surplus hot water is pumped by the micro pump to the base which maintains the top tank stratification when heating a tank from cold or topping up a warm tank. Real time temperature at the top 1/3rd, middle 1/3rd, and bottom 1/3rd of the tank can be displayed so you can understand how much hot water is stored.
Installation procedure.
Tank Device
To speed up installation if is best if an existing tank is left in its normal state with hot water in the top 1/3rd of the cylinder.
Isolate the tank by closing the bottom inlet valve.
Run a tap to drain the pipes above the tank only.
Remove the existing elbow at the top of the cylinder and fit the 4 way cross.
Cut the dip pipe to length with a knife if needed.
Control Device
Set the immersion heater thermostat to 70 deg C which will result in a tank temperature of 65 deg C.
Operation of the Device
The temperature of the hot water cylinder is set by the immersion heater. Please note that an immersion heater set to 70 degrees C will result in a normal tank temperature of approximately 65 deg C. The device will best if you set the immersion heater to 70 deg C or more.
Validation of heating the tank
The original proposal to use Drayton tank thermostats failed in validation. The immersion heater sits in a pocket of hot water and the Drayton tank thermostats is a distance away from the immersion heater. Hot water rises upwards quickly but moves horizontally slowly. The Drayton tank thermostats reacted too slowly and the immersion heater cut out for long periods.
I successfully used temperature sensors to activate ShowerPowerBoosters in 2012 and placing one of these sensors above the heating element gave excellent control of the pumps. The temperature sensor is only required for customers with PV power generation and without the ability to export power to the grid.
The micro pumps are available with both 9 volt and 12 volt input.
For domestic hot water the transformer needs to be set to 9 volts to maintain stratification
For larger central heating tanks the same device is set to 12 volts to remove stratification
Validation 12th May 2024
Temperatures with Immersion heater only
Top 62 Deg C
Top 1/3rd 47 Deg C
Bottom 1/3rd 16.8 Deg C
Temperatures with Energy Storage Device
Top 64.6 Deg C
Top 1/3rd 64.9 Deg C
Middle 62.4 Deg C
Bottom 1/3d 64.1 Deg C
Bottom 65.5 Deg C
Detailed Heating Calculations (18th May 2023)
