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Green Building and Design => Home Automation and Monitoring => Topic started by: shambolic on August 02, 2011, 06:25:01 PM



Title: how can I simply monitor my electricity usage, when I have PV panels?
Post by: shambolic on August 02, 2011, 06:25:01 PM
Hi, I have been reading on here but the more I read the less clear the answer becomes. I am no great techy and so need to ask the question. How can I simply monitor my power usage? I have a power one monitor that tells me the power generated by the panels and I have an EON monitor but it seems like it's not giving a true read out. I don't need accuracy just something that gives a pointer as to what I am using so I can weigh it up against the power coming in. At present I have a meter that actually goes backwards but I am sure they will be changing that as I have informed them about it.

(http://pic50.picturetrail.com/VOL1660/8556180/23316947/397942725.jpg)

The flat grey lead coming in from the top right is where the solar power enters the fusebox


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Donald on September 27, 2011, 04:29:22 PM
I have exactly the same issue. I have free PV panels fitted so I don't care how much they generate. My single focus is on minimising what I pull from the grid because it will cost me money. My little nPower monitor has gone crazy since the PV panels were fitted. I can't believe it's beyond us technically to have a little readout that say, "generating now 2.6kw, being used now 1.5kw, surplus to grid 1.1kw" or "generating now 1.9kw, being used now 2.1kw, pulling from the grid 0.2kw". A little chart would be nice....

Even just a readout that said, "0.2kw being pulled from Grid now"


There must be thousands of people like us, and increasing, who need to know this simple level of detail and I would pay to know this.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Richard Owen on September 27, 2011, 05:34:00 PM
Hi guys,

It's difficult to measure what you want if (as in the picture) the PV panels are connected into the consumer unit.

That's because the meters can't tell in what direction the current is flowing. So, if you're importing 2kW the meter will read 2kW and if you're exporting 2kW, the meter will read 2kW.

There are two ways round it that I see:

Firstly, put a meter on the cable from the panels to the consumer unit or (if your inverter supports it) measure the inverter output. Then do some mental arithmetic to work out the sum (or difference) between the two meters to work out what's going on. Or

Secondly, you could have the cable from the PV panels moved into a Henley Block between the electricity board's meter and the consumer unit. Then, the meter on the consumer unit will only measure consumption and either your inverter, or a meter on the cable from the inverter, will give you the generated amount and the sums get a lot easier.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: CeeBee on September 27, 2011, 06:08:01 PM
As Richard says, if the PV feed goes directly into the consumer unit, then you're left with no cable to clamp monitors on which just carries the load used by the house.

Perhaps I ended up lucky, but (perhaps due to lack of spare slots on the consumer unit at the time) my installers went the way of using a junction box ("Henley Block") where grid/solar/house all meet, and this method does give you separate live/neutral (the ones between the junction box and the consumer unit) which just carry the house load.

When I got a second system somewhere else, I specifically asked them to use the junction box method (which probably entails an extra mini-consumer unit as well) - they said "We're not really supposed to do that, since we have to pull the main fuse to do it." but then it seems all electricians routinely have to pull the main fuse, so they went ahead anyway.

Some other installers I spoke to say they always use the junction box method anyway.

Pleased at least that Richard uses the term "Henley Block" - I thought I was being stupid, as nobody (since those original installers) have recognised the term when I've mentioned it (they've said "We just call it a junction box" or similar).

The Wattson monitor folk have a diagram at http://www.diykyoto.com/uk/wattson (http://www.diykyoto.com/uk/wattson) showing the junction box method. And if you follow the "Click herre to view PDF" from that page, then the PDF shows both possible methods.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Richard Owen on September 27, 2011, 09:43:22 PM

Pleased at least that Richard uses the term "Henley Block" - I thought I was being stupid, as nobody (since those original installers) have recognised the term when I've mentioned it (they've said "We just call it a junction box" or similar).


I call them Henley Blocks as that's what I've always known them as.

I think they are supposed to be called Service Connector Blocks.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Sisso on November 04, 2011, 05:05:28 PM
Hi Guys

Please take a look at my power monitoring system, it can measure if your free solar is greater than the house is using , record the results. It can also wirelessly control two 13 amp appliance sockets and switch them accordingly ie. off when solar is low and on when it is generating more than the house is using.

www.solarcontrol.stuff-4-sale.org

cheers


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: rondurrans on November 04, 2011, 05:15:39 PM
Any suggestion(s) to what they would turn on and off please?................ 149.99...............I think you might be better keeping your money in your pocket and letting the grid have the heavily subsidised clean energy :onpatrol


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: M on November 04, 2011, 05:23:10 PM
Me thinks Martin with an I will be along soon!

Martyn.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Justme on November 04, 2011, 05:26:34 PM
At that price it will take you using every kWh from a 4kWp array for a year to recoup the outlay.

As you could get 30% usage without it you are looking at 2 years till it pays it back at 100% usage. I would bet that 50% would be nearer the mark so 4 years payback. Not to bad but longer than I expected.

How accurate are those clamp on sensors?

What are the other options?

EMMA- to costly
??


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: skyewright on November 04, 2011, 05:47:34 PM
it can measure if your free solar is greater than the house is using
From your web site:
Quote
Another identical unit clamps around your solar power feed.
Many (most?) installations don't have an accessible single conductor available for a CT clamp (especially one that size) to be placed around.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: Sisso on November 04, 2011, 07:31:38 PM
The unit is mainly for people who have had the free panels fitted as they are losing the most money.My home averages 500 watt usage during the day but I generally am generating more than twice that.


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: rondurrans on November 04, 2011, 08:35:27 PM
Sisso what do you turn on?


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: ericw on November 05, 2011, 09:41:54 AM
Sisso what do you turn on?

This is the key question - while it is relatively easy to measure the surplus power being generated, practically using just enough to balance this surplus is much more difficult.
Heating DHW with a series of low power immersion heaters would at first sight seem be an possible answer, unfortunately although 3kw ones can be had for under 20, lower power ones are much more expensive and the solution becomes financially unattrative


Title: Re: how can I simply monitor my electricity usage, when I have PV panels?
Post by: AlanIOW on November 06, 2011, 09:21:17 PM
Hi Sisso

I think your product has great potential, if a little expensive. I note you have no feedback on Ebay for this item, have you sold any yet? I would be prepared to write a review on the item if you were to send one to me for testing - Email me if you are up for it. I do currently have a monitoring system for, both solar PV generation and house consumption, to compare it too on PVOutput.org here; http://pvoutput.org/intraday.jsp?id=2476&sid=1872&dt=20111106

Alan