System Performance Metering [RE-wrenches]

Fri Dec 17 13:17:01 PST 2004

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Jeff,

I think your point about the feasibility of metering smaller systems is 
really well taken.  That's part of what I'm wrestling with myself.  I want 
to see all the systems metered, and the data collected centrally and made 
available.  Unfortunately the current costs of metering and collecting 
performance data on 1-3 KW residential systems, relative to the current 
market value of the power produced, are hard to justify IMHO.  At least 
until the costs of both the additional metering hardware, and the cost of 
meter reading, become substantially cheaper.

My understanding is that many utilities are slowly moving toward automated 
meter reading, using electronic KWH meters that transmit the data through 
high frequency signals coupled on to the power lines.  I assume there must 
be some standard industry protocols associated with that type of data 
transmission, but I haven't done the research to know for sure.  Or maybe 
each utility does it's own thing - it's their power line, so they can do 
whatever they want.

If there are well-developed protocols, I think that perhaps the best long 
term solution is for the inverter manufacturers to incorporate those 
standard KWH metering data transmission protocols into their 
inverters.  (Chris, John, B., don't run screaming for the exits, its just 
an idea, and I'm interested in your take on this whole thing.)   It's 
certainly possible and (I would maintain) it's also the most cost-effective 
solution, at least in theory.  But the political hurdles seem as if they 
might be quite large.

Or maybe something along these lines is already quietly coming together in 
the background, and most of us aren't hearing much about it?

John Raynes
RE Solar
Torrey UT

At 01:12 PM 12/17/04 -0800, you wrote:

>Hey Bill and John and all,
>
>While I  wholeheartedly agree that performance metering is essential to 
>install in any system, tying that data to rebates and getting all that 
>data to a central database and then disbursing those payments is another 
>issue.  In the first round of rebates in Massachusetts they did just that 
>and it's cumbersome.  After experiencing it - many of us at SEBANE -( 
>Solar Energy Business Association of New England) argued against systems 
>less than 10 KW being required to report performance in order to get the 
>rebate.  And don't get me wrong, I actually do want to see some sort of 
>incentive for performance but just how to do it is another question.  We 
>install a lot of tracking systems and I would love to get credit for that 
>extra 25-40% production!
>
>In the first MA round they gave $5.00/watt - $3.50 up front and another 
>$1.50 that you had to prove per KWH over 3 years.  Now that sounds great 
>but don't underestimate the amount of paperwork and hassle that created - 
>and barrier to sales.   Folks weren't psyched to learn they had to carry 
>the money and receive incremental checks. And think of the staff time it 
>takes at the State level.
>
>After seeing the program work on the ground, my recommendation was to 
>offer (or require) performance rebates above a certain size - perhaps 4 or 
>5 KWs or maybe even 10KW so that you would leave out all the small 
>residential systems.  In New England many systems go in at under 3 
>KW.  Many customers go for 1.2-2.4 KW.  1500s are really common.  Another 
>approach would be performance standards as opposed to monitoring.
>
>I contemplated writing up a performance standard system based on modifiers 
>determined at the time of install with no need for subsequent monitoring 
>and reporting for the residential systems.  So you would have a base 
>rebate which you would modify with tilt, angle, and percent shading 
>factors.  It would require some sort of % shading measurement standard 
>equipment better than the Pathfinder as Bill pointed out - but that would 
>be a great addition to our industry anyway (and a product I've long 
>thought someone should produce) - to have a standardized way of verifiable 
>shading percentage reduction. You could also have factors for tracking - 
>for panel types, etc.  The application would get cumbersome but perhaps 
>not as bad in the long run as reporting KWH for years and the CEC having 
>to issue payments over time.
>
>I'd love to see a reported actual data performance system that works and I 
>can see the gathering of the data as easy enough but how to do the 
>payments without hassling the state and the customer?.  MA did make it a 
>honor system based on customer reporting - I think that could work if CEC 
>had a central web reporting system that was really easy.  But a whole 
>system of writing checks based on piddly KWHs from a 2 KW system over time 
>seems like unnecessary bureaucracy to me. There must be a better way 
>and  unless the day comes  when we have modem connected meters everywhere 
>and the utilities process the rebates,  I really think there is merit in 
>the performance standards approach for residential systems and perhaps 
>even commercial systems.
>
>Jeff
>~~~~~~~~~~~~~
>Jeff Clearwater
>Village Power Design Associates
>Sustainable Energy & Water Solutions for Home & Village
>http://www.villagepower.com
>gosolar at villagepower.com
>
>530-470-9166
>877-SOLARVillage
>877-765-2784
>425 Nimrod St.
>Nevada City, CA 95959
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~

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