small solar grid intertie inverters?

[Jason]

Hi,
I was wondering if there is still a small grid intertie
inverter available on the market for the 100 watt range.
I remember there used to be a great and inexpensive one
called the Trace Microsine inverter that was specifically
made for low watt interties, you could plug it directly
in a wall socket in your house to attach to the grid. I
think this model is no longer being made, is there anything
comparable? I don't have the money to start with the
Sunny Boy 700 at $1300 (plus the panels) but i would like
to take what panels I have and start using them as they
are doing me no good in the basement.

thanks,
Jason

 

[William P.N. Smith]

called the Trace Microsine inverter

Unfortunately, those weren't UL-<something> listed, and (except for
the occasional eBay listing) aren't available for sale here any more.
The problem is that UL-<something> testing and certification costs
enough to make the price of the inverter $1000+($0.50/W), so there
aren't any cheap answers.

 

[ptaylor]

it's UL1741 , for the US gridtie certification , and cost run about
50-75K between fees , documentation , paying for UL to witness the
testing , ect.

A company from The Netherlands, NFK , was producing the "OK4U" , which
for a short time in the US was marketed by Trace Engineering (1998-99) ,
but the unit was never certified by ANY major listing either in the US
or UK.

I just checked and it would seem NKF no longer makes the unit and the
OK5U would seem is another vaporware product. There really isn't any
market for inverters in this power range ... gridtie at 100 watts would
be maybe .5kWh day or 182.5 kWh/year .. which at 10 cents kWr would be
18 bucks in electricity / year for a 250 dollar inverter (uncertified) ,
except for a few hobbyists it doesn't make for a profitable market to
sell to.





<http://www.compusmiths.com>

It seems to me that gridtie'ing on a smaller scale wouldn't be worth
it,even if inverters were available.I'd tend to think that a small
solar/batt/inverter setup would be better.That way you can atleast store
some of the power in the batteries,and it will be there for you,day or
night.

I've been using a small 10W panel,and about 45AH of batts to run various
12V appliances in my bedroom (modem,cellphone charger,fans,CCFT
lights,etc) and it's been working fairly well so far for about a year
now.I even have a 300W inverter,that I actually used once when the power
went out one morning.It was enough to finish watching the news on the
TV,and to switch over to the PC (CRT monitor and all) and check my
email,and whatnot. (my modem is on the 12V system,and the cable TV and
telephone lines were still up and working.)I was grinning from ear to
ear. ;-)
Not bad for a small (micropower) PV system.I had the TV,then PC running
for about an hour total,until the power came back.I don't know what the
battery voltage dropped to,but the inverter cutout (10.8V) didn't kick in.

 

[[email protected]]

...UL-<something> testing and certification costs enough to make
the price of the inverter $1000+($0.50/W)...

$1 million for ULing 1,000 inverters sounds very high. I'd guess
it's closer to $50K, ie $50 per inverter, amortized over 1,000.

Nick

 

[[email protected]]

There really isn't any market for inverters in this power range ...
gridtie at 100 watts would be maybe .5kWh day or 182.5 kWh/year ..
which at 10 cents kWr would be 18 bucks in electricity / year
for a 250 dollar inverter (uncertified)...

I'd estimate there's a tremendous market, even with those economics,
and more with a certified $100 600-watt backwards lamp dimmer. Lots
of people think renewable energy is sexy. Think of putting all those
twirling lawn ornaments to better use

Nick

 

[[email protected]]

Well Nick , you are not one to shy from opinions ... It would be nice if
even ONCE , you would back these up with something you actually built.

I've designed and built many things in 40 years of electrical engineering

...my view is based on what three major manufactures have found out ..
even the Sub 1000 watt inverters have a VERY small market...

I have a different view.

If you think there is a "tremendous" market for a 100 watt , UL1741
certified inverter , why don't you design , test , certify and market it ?

I'm more interested in heat energy...

Nick

Many people have heard of Ohm's law in connection with photovoltaics, but
they may not be aware that it also applies to heatflow in houses (with
different units) and that solar heating can be enormously cheaper per peak
watt than solar electricity and that most houses need more heat than electrical
energy (the ratio is 1:1 in Hawaii and 5:1 in Vermont) and that this small
slice of the home energy pie can shrink even further with more efficient
appliances and compact fluorescent bulbs...

Our July 9 workshop on "Ohm's law for heatflow" with applications to solar
water and house heating and natural cooling is partly a basic tutorial
("What is a Btu?"), and partly a discussion of tried and untried schemes
for increasing solar heating fractions ("How much does performance improve
over direct gain if we remove the mass and separate the sunspace from the
living space with an insulated wall and circulate warm air between the
sunspace and the living space during the day and stop the air circulation
and let the sunspace get cold at night?" is a question that can't be
answered with Energy-10...)

We'll provide arithmetic and data and strategies needed to site-build
effective house heating and cooling systems using common, inexpensive skills
and materials like curved 1x3s and polycarbonate glazing. Participants
should be familiar with high school algebra. We'll use calculators to design
houses to be 100% solar-heated in the worst-case month of the year, using
monthly averages from NREL's Solar Radiation Data Manual for Buildings ("Blue
Book.") We would do simple, direct, laptop simulations for various solar
house heating configurations with TMY2 weather data and BASIC or spreadsheet
programs, using simple equations from physics for deep insight.

We'll discuss power, energy, heatflow, and overnight and cloudy day heat
storage at the high-school math and physics level, with insulation values
and heat capacities of materials, time constants, evaporative and nocturnal
ventilation cooling with "smart whole house fan controllers," passive and
low-energy solar heating, superinsulated houses, and ideas for houses that
are 100% solar-heated, by design. Promising techniques include solar closets
and shelfboxes, soap bubble foam insulation, and 2:1 concentrating solar
attics that collect heat and electricity from standard PV panels under
drain-down water-filled lay-flat poly film ducts on the attic floor.

We'll also discuss a simple counterflow greywater heat exchanger, a $60
1"x300' plastic pipe coiled inside a 55-gallon drum. With hot water bursts
of 13 gallons or less, this could be 97% efficient, and maybe illegal, these
days, like Harry Thomason's single-wall galvanized tank heat exchangers.

Handouts will include a workshop writeup on paper and a CD-ROM containing
most of Harry Thomason's patents and writings and the data from NREL's Blue
Book and the paper "Solar Closets and Sunspaces" by Nick Pine and Paul Bashus
and the book Sunspots by Steve Baer and Bill Shurcliff's New Inventions in
Low-Cost Solar Heating book and some pamphlets written by Baer and Shurcliff
and some design guidelines from PE Norman Saunders and the Solar Today stories
"Solar Heat in Snow Country" and "Soldiers Grove Soldiers On" by Nick Pine
and Drew Gillett and some photos of Soldiers Grove and Michael Schofield's
1991 thesis "An Economic Evaluation of Solar Energy at Soldiers Grove."

I'm an EE by training and a registered US Patent Agent. I gave a similar
workshop on 10/4/03 for 20 people at the Sustainable Resources/Engineers
Without Borders conference in Boulder, CO. Steve Baer is a world-famous
solar guru. Rich Komp is president of the Maine Solar Energy Association
and a PV author with a PChem PhD and lots of solar house heating experience,
and Drew Gillett is an ME/CE/PE with architectural training.

Nick

Join solar guru Steve Baer and PE Drew Gillett and PhD Rich Komp and
me for an all-day workshop on solar house heating and natural cooling
strategies ("HVAC Nonsense") on July 9 in Portland, OR--see page 25 of
http://www.ases.org/conferences/2004_call_for_papers/SOLAR2004_prelim_program.pdf

 

[Melodie de l'Epine]

I don't thinks so.... the OK4E 100W inverters by NKF electronics are no
longer distribted,(since December 03) I suspect there was a problem with
the size of market.

(becasue the inverters were pretty stable - even if they weren't cheap,
they were/are useful for building demo kits and display for expos and
RES promotional work.)


Mel

[email protected] a écrit :

 

[[email protected]]

...the OK4E 100W inverters by NKF electronics are no longer distributed,
(since December 03) I suspect there was a problem with the size of market.

They seem to have disappeared from the NKF web site, but IIRC, a few years
ago, there were 4 or 5 European companies working on small grid-tie-only
inverters. I suspect at least one survived, likely in Germany, since I've
heard they pay a lot for PV energy (on the order of 50 cents/kWh) and they
encourage tiny systems. You might look around for small German inverters.

It seems to me that US utilities have always hated the idea of plugging PV
panels into wall sockets, since that cuts into their energy sales. Before
UL-1741, they had to rely on scary stories of frying linemen. Now we have
islanding rules, but it seems to me they are still exerting undue influence
via the NEC to prevent lots of small systems. Why can't we plug a 100 W
inverter into a wall socket, vs a dedicated circuit with its own breaker?

Americans love toys. We have to consider pizazz as well as mundane payback
economics. A recent NPR show talked about coffee beans... there's little
profit and little change in the market in selling mere beans, but grind
them up and and can them a la Maxwell House, and profit margins go up.
Brew the coffee and put it in cups and sell it to people and profits go up
more. Play the right kind of jazz in the background a la Starbucks, and
profit margins go up even further. We're moving into a design economy,
where we sell experiences and attitudes and fun and creativity.

Maybe you've worked in Cubicle Land too long. Creative product designers
might aim to help people feel more bubbly and ecological *all over*, with
more meaningful lives.

We *cannot* sell people on being uncomfortable and worried and cheap. We
have to make it sexy, trendy, easy, cool, hip, frugal, whatever other word
you want to use. Something that looks like a trendy version of an existing
appliance might work. Very few people want the experience of being an
accountant, a subsistence farmer, a monk, or a passenger on a leaky boat.

Nick

 

[Jason]

Thanks to all who have replied with all the great information.
Good to get a dialogue going. Sorry to hear that they are no
longer available, i guess I just have to save up for the Sunny
Boy. I do disagree that there could be no market for the small
inverters- i realize that on that scale ( < 100W ) there is no
great economical benefit, but if people could go out to a store
and buy a panel/inverter combo for $150-$200, just to chip in
and do their part for cleaner energy, i bet more than a few
would do it. especially if all they had to do was plop it out
in the sun and plug it in the wall. Real Goods makes a mint
off of high priced "feel goody" sustainable products. i'd bet
this would fit right in. Thanks for your input everybody!

Jason

 

[Chuck Yerkes]

Thanks to all who have replied with all the great information.
Good to get a dialogue going. Sorry to hear that they are no
longer available, i guess I just have to save up for the Sunny
Boy. I do disagree that there could be no market for the small
inverters- i realize that on that scale ( < 100W ) there is no
great economical benefit, but if people could go out to a store
and buy a panel/inverter combo for $150-$200, just to chip in
and do their part for cleaner energy, i bet more than a few
would do it. especially if all they had to do was plop it out
in the sun and plug it in the wall. Real Goods makes a mint
off of high priced "feel goody" sustainable products. i'd bet
this would fit right in. Thanks for your input everybody!

Chipping in involves more than a couple months of my power bill.
For it to be worth while to bother with, yeah, it's going
to be a real investement.

The simple fixed RAW COSTS for an inverter and panel - the
metal, the glass, the plugs, the testing never - make it
such that doing it at 100watts wouldn't cost a whole lot
less than 1000watts.

So then lets add in distribution, plus permitting to even
HAVE the intertie (and the kill switches you should have) and
it's not worth playing the game for the power of pair of lights.

If you're intent, then a panel can feed a battery and you can
use it for a separate circuit.

 

[William P.N. Smith]

Boy. I do disagree that there could be no market for the small
inverters- i realize that on that scale ( < 100W ) there is no
great economical benefit, but if people could go out to a store
and buy a panel/inverter combo for $150-$200

But at the current prices for inverters (say a buck a watt) and panels
($4-10/watt) it would be more like at least $500 for that combo, which
does tend to limit the market, even with a 3-year (best-case) payback.

 

[Melodie de l'Epine]

I agree that the market may be to small at the moment, but I'm not sure
the lack of payback is the issue. I think it's the price itself -
I mean, if it cost 50€ and had a payback time of 35 years I think it
would sell better than if it cost 250€ with a paybak time of 10 years)

....because the amount of energy produced is more symbolic than anything.


Other issues can also make it difficult - here in France you cannot
"plug in" unless you have a grid connection contract, and a meter
installed by the grid manager etc.... with a delay of about 12 months
and a cost of 300 to 1000 euros (1 euros is approx 1$US). So it's really
not worth the hassel.

mel


William a écrit :

 

[Pom-pom-pom]

I agree that the market may be to small at the moment, but I'm not sure
the lack of payback is the issue. I think it's the price itself -
I mean, if it cost 50€ and had a payback time of 35 years I think it
would sell better than if it cost 250€ with a paybak time of 10 years)

...because the amount of energy produced is more symbolic than anything.


Other issues can also make it difficult - here in France you cannot
"plug in" unless you have a grid connection contract, and a meter
installed by the grid manager etc.... with a delay of about 12 months
and a cost of 300 to 1000 euros (1 euros is approx 1$US). So it's really
not worth the hassel.

mel

A better marketing approach would be to sell it as a new hitech fashion.
Compare it with those large flat TV screen. They are VERY expensive and most
people look only jerk tv-shows on them. What a waste!
These tv will never payback in term of "actual quality"/"price". But their
owners are proud to display them in their living-rooms.

Now if it were so chic to display a solar panel on one's roof, then many
rednecks would take a loan to buy it. They would challenge between them a la
"My panel is bigger than yours".

How to achieve this? If I were the marketing director of BP solar; I'd pay
some movie-star to ostensibly show his/her new panel.
Even better, I'd pay whatever it takes to have one built on 'La ferme
célébrités'* by the players themselves. If THEY can do it, anyone can.
Add a general blackout with the help of Bin Laden, and you sell like crazy.

pom-pom-pom


* = Paris Hilton show, shobiz stars in a farm