OP
Duplada
My first post here, though I have been reading this thread since I had my 3.84kw PV system installed last November. The reason for my post is to give those of you who are considering using your excess PV to power your immersion heater, insight into some of my experiences using manual switching and using a proportional device. After reading this thread from start to finish, when it originally had over 50 pages, it soon became apparent to me that a proportional solution was the way to go, because as far as I could see, all the other none proportional solutions had the possibility of importing more electricity than you were trying to save.
Since I first had my PV system installed I have monitored my PV generation with a SunnyBeam, my true house load with a clamp sensor on a Current Cost ENVIR Monitor (via a /Henley Block) and also my real time energy import with an Optismart reader on another Current Cost ENVIR monitor. These days, the data from these devices is output and recorded in an SQL database before being uploaded to one of the PV statistics sites. This setup allows me to see the true house load on one monitor and to see instantly if I am importing or exporting on the Optismart monitor. The Optismart monitor counts the pulses generated from the Electricity meter and is very accurate indeed, it shows zero when you are exporting. When you are importing the Optismart shows your true import and the difference between the house load monitor and the Optismart is your real time generation, which of course can be confirmed on the Sunnybeam generation monitor.
Finally to the reason for telling you about all these monitors, I work from home and with them sat on my desk it was difficult not look at them constantly. Monitoring my ever changing power status this way, enabled me to manually switch on washing machines, tumble dryers, dishwashers etc in sequence when sufficient power was available. I managed up to the end of February this year and was using about 70% of the power I generated. When March arrived with numerous sunny days (remember those) resulting in daily generation in excess of 22KW it was very clear that I could not mop up all the available excess power. By lunch time I had done two loads of washing two loads of tumble drying and had run the dishwasher and was now exporting again, with nothing left to run. My PV panels are at an inclination of 22 degrees so I do not generate over 3KW until the end of March. Therefore firing up the Immersion heater (3KW) would have meant also importing prior to this date, so up until the end of March the Immersion heater was not part of the manual load switching. Even when I could fire up the Immersion heater without importing I was forever having to switch it off again as it clouded over. In fact managing all this excess power was becoming a full time job and it was driving me nuts.
I therefore decided for my sanity that I had to get hold of one of these proportional controllers that dumped any excess into the Immersion, so that I could mop up any excess over my base load. If you have the means of monitoring your consumption and generation in real time like I have, you will have noticed that very often in particular on cloudy days, or early and late in the evenings, there can be a continuous small excess of say 300 to 500 watts, it is more or less impossible to mop up this excess without a proportional controller, and it adds up to quite a lot of export over an entire day.
Since I am not a electronics wizard building my own unit was out of the question for me. I managed to get hold of a kit manufactured by Echase a regular poster here. At the time (April 2012) he was handing his design over to a company for commercial production and had a few kits still for sale. To get the kit I had to sign a non-disclosure agreement, so I can’t talk about how much it cost its design etc. Though I don’t think Echase will mind me telling you that it is a very professional unit and works very well indeed. As I understand it, the same commercial unit that I have, can be purchased from Engesa with a PV system, but it is going to be available to purchase on its own, if enough people enquire about it. I think its commercial name is Solar24. I would also like to point out that I have no connection with either Echase or Engesa,
The unit connects between your consumer unit and your immersion circuit, there is no configuration whatsoever, you switch it on and it just works.
I have had the unit installed and operational now for over two and a half months and the unit is mopping up around 90% of my excess power. The unit exports a very small amount of power and never imports when a load changes (I can see this on my OptiSmart). It typically sorts out the new export value in about a second or two, if the load changes (kettle switched on) or a cloud appears to lower generation, but it never imports which is quite remarkable. Since the beginning of May when I completed the unit, my GAS central water heating has been off. I have only had to heat the water twice during this period, due to consecutive days of very poor weather. I have very detailed records of my GAS usage and during the two and half months I have had the unit in operation I have saved about £25 in GAS. I am quite satisfied with this; it will obviously be lower in winter but nevertheless a good saving.
There are one are two things I can point out to help you maximize the amount of excess power you can mop up. My hot water tank is a big one nearly 2 meters tall and holds 240 liters. However, my Immersion is only just under a meter in length. Therefore, I am only heating half the tank, this takes about 7KW to heat from cold but typically takes less on a daily basis as the water is not cold. To maximize the amount of water I can heat in my tank, and the excess export I can use, I am using a low voltage pump and two thermostats to circulate the water in the tank, to automate the process of heating a full tank.
On really sunny days (joke) my system can generate about 29KW so even after heating my big tank of water and running every white goods device to hand, I can still end up exporting 6 to 9KW. The real benefit though is I no longer have to think about the excess PV on most days, my proportion device just takes care of heating the water which is lowering the amount I spend on GAS. The other big asset is that I am no longer rushing around the house performing sequential domestic appliance management and have got my life back.
If you have managed to read this far you deserve a medal, and I promise not to post again. Though my advice is, if you want to have an easy life, and save money, then invest in a proportional device.
regards
Since I first had my PV system installed I have monitored my PV generation with a SunnyBeam, my true house load with a clamp sensor on a Current Cost ENVIR Monitor (via a /Henley Block) and also my real time energy import with an Optismart reader on another Current Cost ENVIR monitor. These days, the data from these devices is output and recorded in an SQL database before being uploaded to one of the PV statistics sites. This setup allows me to see the true house load on one monitor and to see instantly if I am importing or exporting on the Optismart monitor. The Optismart monitor counts the pulses generated from the Electricity meter and is very accurate indeed, it shows zero when you are exporting. When you are importing the Optismart shows your true import and the difference between the house load monitor and the Optismart is your real time generation, which of course can be confirmed on the Sunnybeam generation monitor.
Finally to the reason for telling you about all these monitors, I work from home and with them sat on my desk it was difficult not look at them constantly. Monitoring my ever changing power status this way, enabled me to manually switch on washing machines, tumble dryers, dishwashers etc in sequence when sufficient power was available. I managed up to the end of February this year and was using about 70% of the power I generated. When March arrived with numerous sunny days (remember those) resulting in daily generation in excess of 22KW it was very clear that I could not mop up all the available excess power. By lunch time I had done two loads of washing two loads of tumble drying and had run the dishwasher and was now exporting again, with nothing left to run. My PV panels are at an inclination of 22 degrees so I do not generate over 3KW until the end of March. Therefore firing up the Immersion heater (3KW) would have meant also importing prior to this date, so up until the end of March the Immersion heater was not part of the manual load switching. Even when I could fire up the Immersion heater without importing I was forever having to switch it off again as it clouded over. In fact managing all this excess power was becoming a full time job and it was driving me nuts.
I therefore decided for my sanity that I had to get hold of one of these proportional controllers that dumped any excess into the Immersion, so that I could mop up any excess over my base load. If you have the means of monitoring your consumption and generation in real time like I have, you will have noticed that very often in particular on cloudy days, or early and late in the evenings, there can be a continuous small excess of say 300 to 500 watts, it is more or less impossible to mop up this excess without a proportional controller, and it adds up to quite a lot of export over an entire day.
Since I am not a electronics wizard building my own unit was out of the question for me. I managed to get hold of a kit manufactured by Echase a regular poster here. At the time (April 2012) he was handing his design over to a company for commercial production and had a few kits still for sale. To get the kit I had to sign a non-disclosure agreement, so I can’t talk about how much it cost its design etc. Though I don’t think Echase will mind me telling you that it is a very professional unit and works very well indeed. As I understand it, the same commercial unit that I have, can be purchased from Engesa with a PV system, but it is going to be available to purchase on its own, if enough people enquire about it. I think its commercial name is Solar24. I would also like to point out that I have no connection with either Echase or Engesa,
The unit connects between your consumer unit and your immersion circuit, there is no configuration whatsoever, you switch it on and it just works.
I have had the unit installed and operational now for over two and a half months and the unit is mopping up around 90% of my excess power. The unit exports a very small amount of power and never imports when a load changes (I can see this on my OptiSmart). It typically sorts out the new export value in about a second or two, if the load changes (kettle switched on) or a cloud appears to lower generation, but it never imports which is quite remarkable. Since the beginning of May when I completed the unit, my GAS central water heating has been off. I have only had to heat the water twice during this period, due to consecutive days of very poor weather. I have very detailed records of my GAS usage and during the two and half months I have had the unit in operation I have saved about £25 in GAS. I am quite satisfied with this; it will obviously be lower in winter but nevertheless a good saving.
There are one are two things I can point out to help you maximize the amount of excess power you can mop up. My hot water tank is a big one nearly 2 meters tall and holds 240 liters. However, my Immersion is only just under a meter in length. Therefore, I am only heating half the tank, this takes about 7KW to heat from cold but typically takes less on a daily basis as the water is not cold. To maximize the amount of water I can heat in my tank, and the excess export I can use, I am using a low voltage pump and two thermostats to circulate the water in the tank, to automate the process of heating a full tank.
On really sunny days (joke) my system can generate about 29KW so even after heating my big tank of water and running every white goods device to hand, I can still end up exporting 6 to 9KW. The real benefit though is I no longer have to think about the excess PV on most days, my proportion device just takes care of heating the water which is lowering the amount I spend on GAS. The other big asset is that I am no longer rushing around the house performing sequential domestic appliance management and have got my life back.
If you have managed to read this far you deserve a medal, and I promise not to post again. Though my advice is, if you want to have an easy life, and save money, then invest in a proportional device.
regards
