So now I have a solar PV system how do I make the most of it???

Hobbo2006

zeupater wrote: »

... too right ...... by the time you've factored in a qualified electrician's hourly rate you could really count on doubling the base cost of the units ... reading instructions, cabling from the inverter and/or consumer unit, installation, testing, provision of relevant paperwork, drinking half a dozen mugs of tea, etc ....

Z

The Immersun estimate included installation as they are only going to sell through installers. So only your own mugs of tea to account for whilst you keep an eye on the LCD screen. :-)

I waiting with interest to see what happens when they release the product to the installers. Only then will we know what the final cost will be.

sly_dog_jonah

I sent an email enquiring about the immersun last Friday, and got a response pretty quickly.

I've been researching this topic for a while but have yet to find a compelling product with a reasonable payback period. So I would be interested to hear more from you.

Here's our situation:
- house is 18months old, so condensing gas boiler is very new.
- we have 3.7kWp array on an SE unshaded roof
- system ISN'T wired via a henley block, the PV connects directly to a switch on the CU (via a generation meter and isolator of course). It's therefore not easy to current clamp the mains supply, unless this is done outside the house within the meter box (nearby where the CU is in the hallway).
- import meter is a digital meter, and LED stays on when exporting.
- we have a GEO Solo PV monitoring output of the generation meter via an LED sensor. Generation meter LED stays on when PV is not generating.
- Inverter is an Enfinity model and has little or no useful connectivity
- immersion is on it's own dedicated circuit on the CU (generation meter is on the other side of the wall)
- 200litre water tank is heated by Gas boiler, or by 3kW immersion (currently I only manually switch this on on really sunny days)
-Hot water out ISN'T downmixed with a thermostatic mixing valve to a safe temperature, so both thermostats are set relatively low. Haven't explored whether a TMV might be an option to retrofit, imagine it can't be much effort since there is mains cold water in the airing cupboard? With one toddler in the house and a bun in the oven we don't want to set the thermostat any higher unless we get a TMV.
- Hot water usage via gas is around 13-15kWh/day, based on our summertime usage (when central heating is off). (Typically 2 showers and a shallow bath per day). Washing machine and dishwasher are supplied with cold water.
- Ideally I want any kit installed in the airing cupboard (upstairs) rather than the study/hallway where the generation meter/CU is sited (downstairs).
- We are currently pay a standing charge for our gas, but am aware that if we can reduce our gas usage sufficiently we may be able to save money by getting a NSC tariff.

Here's the reply I got from them, posted for the benefit of others considering the product who find their website a bit lacking in the detail:

In most cases the immerSUN is best located near the consumer unit as access to immersion feed, supply power and incoming mains is simple.
The current sensing clamp which goes around the incoming mains supply can be positioned inside the consumer unit, or on the meter tails.
It this is not acceptable, you could wait for our wireless sensor add-on which will be available in about two months time.


With you having a reasonable size PV array and hot water cylinder, the immerSUN will work very well.
Your system should give a yield of around 3100kWh per year, assuming that 70% of that is exported to the grid, that leaves 2170 kWh available to heat water. (That's about twice that of a domestic solar thermal system by the way).
So with your estimated hot water usage of 13-15kWh per day (say 14kWh), that's 5110kWh per year. Therefore the immerSUN could meet almost half of the hot water demand, which equates to a saving of around £200 p/a at 10p per kWh.
We have priced the immerSUN, so that it is possible to have the unit installed for £500 - £600. This means your estimated payback should be 3 years.




More information about the immerSUN...


[FONT=arial, sans-serif]There are several "solar switches" available that imply they do likewise. However, what sets the[/FONT] immerSUN ap[FONT=arial, sans-serif]art from the rest is that it is not a switch that requires 1kW before it puts power to the immersion. Instead it modulates all excess power from as little as 30 watts. Meaning very close to 100% of generated power can be used. This is the clever bit which we feel makes our product unique and will produce significant savings for the end user. For the majority of customers, the switch type products of our competitors quite possibly won't pay for themselves during the lifetime of their PV array. We believe ours will typically do so in approximately 3-5 years.[/FONT]


Here's just a few features of the immerSUN ...

• Simply heats water from your PV system or Wind Turbine
• immerSUN uses 100% of the generated power from a Wind Turbine or Photovoltaic system to heat water ensuring an increase on the initial investment
• Unlike many competitors, it modulates the power to the immerSUN no matter how little - This is not a switch
• Effectively adjusts power levels to the immersion heater, keeping the exported power at virtually zero
• Does not require a set amount of generated electricity (e.g 1kW) before it feeds the immersion
• The most cost effective system available with a non invasive, simple installation
• The consumer no longer needs to be at home to use the free electricity, whatever the weather
• Simple to install, retrofit or with new system
• No need to change the immersion heater
• No minimum system size required
• Suitable for all electrical microgeneration systems
• Back-lit LCD display shows energy saved, output power and operating mode
• Dual immersion heater control option
• Can be daisy-chained for multiple loads
• 3 Year Product Warranty

I've replied to them querying the calculations, specifically that:

• The cost of Gas is more like 3.5-4.5p/kWh, not 10p/kWh, which makes for a much longer payback period (6-7years).
• Smart Meter roll out and accurate export metering (instead of 50% deemed) will reduce the savings by 3.2p/kWh. Most customers would likely get a smart meter within the payback period and therefore extending the length of it as the savings per kWh will be significantly reduced.
• That reducing exported electricity to nil (by using the rest of the 70% generation) assumes that the hot water tank has an unlimited capacity.

I also just asked the following, awaiting their reply:

If the device can be priced at an installed cost which provides us a likely payback period of ~3 years then I would be interested to know the following:

1. Can the device be overridden to force the immersion on at full power (i.e. use import electricity)? For example in a snowstorm in mid-winter and the boiler packed up and we had no hot water.
2. What are the dimensions of the device?
3. How much will the wireless sensor cost, if needed?
4. Does the display only show energy saved on the current day, or does it have a weekly/monthly/lifetime counter as well?

jkpaul

Hi,
sorry if this has been covered elsewhere, but I've searched without luck to find the answer to this question [I've been ploughing my way through this thread from P1 - P84 (so far) ... tough going at times with all the trolling]:

I know the manufacturer's quoted efficiency levels for my panels, but don't know whether this is what I need to put in the system losses box on the PVGIS website.

I've used the default (14%?) until now and it seemed to work well, if be a little below par until now (although April, June & July have been disappointing - weather-related I think):

• Dec - 124% of PVGIS achieved
• Jan - 134% "
• Feb - 120% "
• Mar - 140% "
• Apr - 89% "
• May - 109% "
• Jun - 91% "

July so far is @ 90% of PVGIS (for 22 days elapsed) ... pitiful!

We have JA Solar panels (16 x 250W - JAM6-60-260/Si) and a Fronius Inverter (IG TL 3.6).

• Do I need an efficiency / losses figure for the Inverter too?
• What about cabling etc. to cover the whole system?!
• Are the efficiency figures relevant / equivalent to this losses question?

Sorry for any stupid questions ... ... !

sly_dog_jonah

Panel efficiency is the ability of the panels to convert solar radiation into useful DC current. The PVGIS site makes assumptions based on the panel type to estimate this. This is based on long term climatic data, not this year's weather.

System losses are the combined inefficiencies in converting that DC current into useful AC current for use in the house. Unless you know better, 14% is a pretty good assumption unless you have very short DC strings, a very high efficiency inverter and/or a short AC path to your consumer unit.

If you want to compare your system against actual weather conditions, there is a useful site which requires registration: http://solargis.info/pvspot/index.htm Edit: it now requires a license fee (undisclosed) to get accurate data, damn!

Our current generation this calendar year compared to PVGIS is as follows:

Jan +26.25%
Feb +21.88%
March +49.63%
Apr +8.90%
May +13.69%
June -4.67%
July -34.27% (but with 9 days of glorious British summer ahead?!?)

jkpaul

Thanks very much for that.

sly_dog_jonah wrote: »

July -34.27% (but with 9 days of glorious British summer ahead?!?)

Let's hope so!

I had also been watching the SolarGIS data for my installation, but was also disappointed last week to see they've implemented the fee ... € 120 EUR + VAT for 12 months :mad: at least the MetOffice gives some interesting retrospective weather info, even if it is only monthly.

I think I'll stick to the 14% figure, thanks.

sly_dog_jonah

jkpaul wrote: »

Thanks very much for that.



Let's hope so!

I had also been watching the SolarGIS data for my installation, but was also disappointed last week to see they've implemented the fee ... € 120 EUR + VAT for 12 months :mad: at least the MetOffice gives some interesting retrospective weather info, even if it is only monthly.

I think I'll stick to the 14% figure, thanks.

Ouch, well that isn't worth it then for residential installations.

jkpaul

sly_dog_jonah wrote: »

Ouch, well that isn't worth it then for residential installations.

Indeed, sadly not

Cardew

sly_dog_jonah wrote: »

I sent an email enquiring about the immersun last Friday, and got a response pretty quickly.




The cost of Gas is more like 3.5-4.5p/kWh, not 10p/kWh, which makes for a much longer payback period (6-7years).

• Smart Meter roll out and accurate export metering (instead of 50% deemed) will reduce the savings by 3.2p/kWh. Most customers would likely get a smart meter within the payback period and therefore extending the length of it as the savings per kWh will be significantly reduced.
• That reducing exported electricity to nil (by using the rest of the 70% generation) assumes that the hot water tank has an unlimited capacity.

Excellent post!

If you have gas, the savings are costed as you say. If you have only electricity - you surely heat water with E7.

I wonder what proportion of properties have a combi anyway.

There is the assumption from the manufacturer that the HW tank immersion will always be able to use the available surplus electricity - i.e the water will never be up to temperature. Of course some days you will have over 20kWh surplus - other days none.

sly_dog_jonah

Cardew wrote: »

Excellent post!

If you have gas, the savings are costed as you say. If you have only electricity - you surely heat water with E7.

I wonder what proportion of properties have a combi anyway.

There is the assumption from the manufacturer that the HW tank immersion will always be able to use the available surplus electricity - i.e the water will never be up to temperature. Of course some days you will have over 20kWh surplus - other days none.

Yes I imagine E7 or Oil for water heating is used in the absence of gas, the former being the cheaper I suppose. However as per my email, they knew we used gas to heat a 200litre tank and provided the payback estimate I quoted.

According to Worcester-Bosch:

combis now account for well over half of all the new domestic boilers installed in Britain every year.

Unless the immersion thermostat is set very high, we'd struggle to NOT hit that temperature on a good day, even if the tank was cold in the morning. Even then on record days we'd hit 90C based on my calculations, meaning some electricity would be exported. We'd also need a mixing valve to reduce the temperature at the taps (which conserves the hot water so the tank would last longer). On a dismal day, when generation can be as low as a couple of kWh's then we'd have to supplement the heating with gas (unless there is adequate stored hot water from previous days).

zeupater

sly_dog_jonah wrote: »

Yes I imagine E7 or Oil for water heating is used in the absence of gas, the former being the cheaper I suppose. However as per my email, they knew we used gas to heat a 200litre tank and provided the payback estimate I quoted.

According to Worcester-Bosch:



Unless the immersion thermostat is set very high, we'd struggle to NOT hit that temperature on a good day, even if the tank was cold in the morning. Even then on record days we'd hit 90C based on my calculations, meaning some electricity would be exported. We'd also need a mixing valve to reduce the temperature at the taps (which conserves the hot water so the tank would last longer). On a dismal day, when generation can be as low as a couple of kWh's then we'd have to supplement the heating with gas (unless there is adequate stored hot water from previous days).

Hi

Something which you would need to consider is the use if the immersion when you're not generating. The higher the temperature is set the higher the background heatloss/day from the cylinder therefore don't heat to the high temperatures if you're not using solar as the source ... best to have the gas-fired thermostat set to normal and the solar temperature set to the higher setting (90C may also be a little high and may lead to a massive increase in limescale buildup in the cylinder if you have hard water), you'll also need to check the spec of the TMV for the max operating temperature. Setting the timer for the gas boiler to heat the water in the evening will ensure that the gas would top-up the cylinder if it's been a dull day ...

HTH
Z