||||| Photovoltaic Questions For Home Installation

 Looks like weâ��ll be installing a photovoltaic system for our home in
Berkeley.  And now Iâ��m confused at a higher level.  But thatâ�=
�s
usually the case.��I think we�ll end up with a 4 ba=
ttery backup
system which should cover most, if not all, our needs.  The number of
PV cells we can install is somewhat limited by the topography
(skylights, vents, etc.) of our roof.��So.. here are some o=
f the
things Iâ��m confused about.  Email on list or directly to
ira@berkeleyhomes.com if you wish.

WHAT KIND OF METERING?

metering:â�¨Bi-Directional:    The meter runs forwards and
backwardsâ�¨Time of Use:        The meter places higher dollar value on tim=
es
of high demand��Does PG&E just look at the net kwh (in-out)=
 or the
value of the net kwh (electricity generated at high demand is valued
higher than electricity at low demand?
My thoughts:  Go with a Time-Of-Use meter.

IF WE "ZERO OUT" ... AND BECOME A NET GENERATOR CAN I GET PAID BY PG&E?
If I read the PG&E link correctly, then it may be possible to generate
more than I need, and sell it back to PG&E.  This is not a major
consideration, except in deciding how many panels to install.
If I the best I can do is �zero out� the bill, then it does=
n�t
make sense to get more panels than I need.  If I can make money
�selling� electricity, I�d be curious to find out i=
f it makes
financial sense to do so.  Why spend more money to get more panels than
needed if there�s a limited return.
So... is it possible to get a check from PG&E, or is the best I can
expect is a zero bill?
What do you recommend?

OUR USAGE
Jan-Mar 2006 we�ve been using about 1,400 kwh for the month. The mo=
st
amount of electricity we�ve used over the past two years for home &
office was 1,572 kwh.  â�¨â�¨Should we size the number of panel=
s based
on current, peak or peak + future additional usage?  Or simply based on
the averaged usage per month/year?  We might have some increase in
usage over the next few years (electric golf cart, larger TV, etc... )
but I don�t anticipate huge changes.��With net mete=
ring, does it
make a difference, or should we simply design to zero-out for the year?
 Feed more into the system in the summer at higher rates, draw off it
at night and during the winter��

PG&E READING
Some sites say you get monthly reports and annual bills.  What is your
experience?



BATTERY BACKUP
I�d always assumed that the panels feed the batteries during the
day...��My inclination is to go with 4 batteries rather tha=
n 8, but
am still confused as to what 4 batteries will actually run
overnight.â�¨â�¨Do you have an easy way to evaluate it?  For ex=
ample,
will 4 batteries run an 8.2 amp refrigerator plus 4 100 watt bulbs for
a long December night?��From what I understand, the battery=
 backup
goes to one dedicated circuit.  â�¨â�¨Is that circuit then take=
n from
the main circuit panel?�

PHOTOVOLTAIC CELL & BATTERY LIFE
What should I expect for the life of the photovoltaic cells and
battery?��

INSTALLATION ANGLE EFFICIENCY
We want to be good neighbors with our neighbor to the north, so would
consider installing PV cells as a less-than-optimal angle.  We have a
flat roof, and want to make the framework less unsightly.��=
I assume
that there is an optimal angle to install the panels at.... and a
minimum angle to insure rain washes the panel clean.  How much
difference is there in efficiency at different angle?



NON-BATTERY BACKUP SYSTEMS
Since we�re installing a battery system, this doesn�t affec=
t me...
but I seemed to see conflicting information regarding systems without
battery backup.  One says that photovoltaic is designed to SHUT DOWN
until utility power is restored, the other says that it simply
disconnects from the grid during a blackout (and presumably still feeds
the house) during a blackout.��So.. if you have a system wi=
thout a
battery... does it provide electricity when the grid goes down?  Iâ��d
assume that was true.. but now I�m not sure.��I rea=
d in �A
Guide To Photovoltaic System Design and Installation
â�¨http://www.energy.ca.gov/reports/2001-09-04_500-01-020.PDF    â �=
¨â�¨2.1.1.
Grid-Interactive Only (No Battery Backup)
This type of system only operates when the utility is available. Since
utility outages are rare, this system will
normally provide the greatest amount of bill savings to the customer
per dollar of investment.
However, in the event of an outage, the system is designed to shut down
until utility power is
restored.

According to the City of Berkeley web site, there are two kinds
http://www.cityofberkeley.info/sustainable/residents/ResSidebar/FAQRenewabl=
e.html
â�¨1)    Utility â��inter-tieâ�� system connects to the grid=
 but
disconnects from it when the grid goes down in     a blackout or seismic
eventâ�¨2)    Stand Alone System - completely independent from the grid
They also say the following... which seems inconsistent:
Is there a way to sell my excess power back to my utility company?
     Yes; this is called �net metering�=
.  Beware that it is
not as profitable as you might think.  Here�s why: only utilit=
ies
formed before January 1, 1998 are obligated to purchase your excess
power.  If your utility is one of the newer ones formed recently, they
are not obligated to purchase it.  Older utilities must purchase it,
but they will only pay you their wholesale cost, not the retail cost
you pay them when you use electricity.  Additionally, you must sign a
Net Metering Agreement form before you begin to generate power. 
 
What about my excess energy?  Will my utility pay me for energy I
produce but don't use?
    No.  Your utility will "store" your excess energy f=
or your use
at night time or on cloudy days when you use more energy than your
system can produces.  The Net Metering agreement will balance your
energy production over your energy use for one calendar year, and any
excess energy you produce will be voided.  You will not be paid for
this excess energy, so your system should be sized very carefully.

  Ira Serkes wrote:

Do you have a lot of blackouts? Do you have a backup generator
or backup batteries now? Do you absolutely need electricity
even when the grid goes down?

My thoughts on this is that Berkeley is likely very civilized
and the grid is probably both very reliable (less than two
blackouts a year) and has priority for repairs when it does
go down. You likely do not need a large battery system.

You may want a UPS or two, or perhaps a small generator, for
emergencies. They make small propane/natural gas generators
for fridges and freezers that will automatically start when
the grid goes down and keep things cold. Keeping food from
spoiling is typically one of the few uses a normal household
has for emergency electricity.


You might not have any choice on this. Here in the land of
LADWP they do not allow time-of-use metering when you are
selling power back to the grid. Net metering is typically
the best deal you can get.


Typically, in California, any excess (negative amount) after
12 months gets donated to your power company. If you do manage
to get paid by PG&E you may find they do not pay retail rates
but a much lower number. You're not going to make money selling
solar PV power. You're not likely to even break even unless you
get some kind of grant or buydown from the government.


If you are grid-tied then it doesn't really matter how big your
panels are. Buy as much as you feel comfortable spending.


I'm not with PG&E bug with LADWP they bill you just like everyone
else with the exception that the power meter spins both ways and
after 12 months any negative amounts get zeroed. There is still
the minimum billing amount (less than $10) which you have to pay
regardless of how much power you use or generate.


Saying 4 or 8 batteries doesn't mean anything. Batteries come in
different sizes and capacities. 4 AAA batteries do not store as
much electricity as 4 golf cart batteries.

I'm of the opinion that you probably do not need batteries.


PV cells should last their warranty period (25 years) plus some.
The plus some is a wild card but most folks generally feel they
will last upwards of 50 years and maybe twice that. They will
steadily decline in production though so after 25 years you may
only have 80% to 90% of their original rating and after 75 years
they may only be producing half. After 100 years you may want
to simply donate them to someone else and buy something better.

Batteries vary wildly. Treated right, they can last decades.
Generally 5 to 10 years is a reasonable expectation.


Most grid-tied inverters shut down entirely when the grid goes
down. No grid, no power, no matter how bright the sun is. This
is typically not much of a problem because in most places the
grid is fairly reliable.

There are inverters which will produce power without the grid
but they are somewhat more complicated to install and you need
batteries.

Anthony

 ANTHONY:
Do you have a lot of blackouts? Do you have a backup generator
or backup batteries now? Do you absolutely need electricity
even when the grid goes down?

IRA:
Blackouts are rare - Once or twice a year would be rare.

For batteries, I'm thinking more of earthquake driven blackouts...
having Electricity coming in from the PV Cells and also keeping a
refrigerator/some lights/flashlights/radio/walky talky/cell phone being
recharged.

I do have numerous small UPS boxes for computers.  This PV project
started after watching New Orleans after Katrina.. not quite a sneak
preview of Berkeley after the earthquake... but close enough.

We could even bring our "neighborhood watch" group back to life and
become a central location for neighbors to keep any medications safe,
cell phones and batteries recharged, etc.


ANTHONY:
Saying 4 or 8 batteries doesn't mean anything. Batteries come in
different sizes and capacities. 4 AAA batteries do not store as
much electricity as 4 golf cart batteries.

I'm of the opinion that you probably do not need batteries.

IRA:
Good points about the size of batteries.  I guess my question really
should be.... If I get 4 batteries so that I can run a refrigerator (8
amps?) overnight plus lamps, any guidelines on what the battery specs
should be.

Since it was not obvious to me that when the grid goes down, PV systems
also go down unless you have a battery system... I'm leaning towards
the idea that anyone installing PV should ALSO install a small battery
system if they can afford it. It's kind of like an insurance policy on
their PV system... keeps it running regardless of the status of the
grid.

I'd always assumed that one benefit of a PV system was that it provided
electricity even if the grid went down.  I'll bet that most consumers
would make the same, incorrect, assumption!

Generator systems - also a very good alternative... but we have a
fairly small lot and I'd prefer to not keep fuel on it.  Plus... if the
grid is down, and the fuel runs out... the generator would de-generate
(so to speak)


ANTHONY
PV cells should last their warranty period (25 years) .... After 100
years you may want to simply donate them to someone else and buy
something better.

IRA
After 100 years... I'll be past my warranty and hopefully usable parts
donated to someone else!

ANTHONY
Most grid-tied inverters shut down entirely when the grid goes
down. No grid, no power, no matter how bright the sun is.

IRA
Certainly not what I would have expected!

THANK YOU

 I have a small PV system here with about 400 AH of battery backup.
 I use it to run my ham radios and charge my cell phones and lap top via a
small inverter.
 For what it seems you want I think that a couple of golf cart batteries.
Maybe 90 watts of solar panels (to start with and see how it goes from
there)
 A small charge controller.
 A small inverter, sat a 300 or 400 watt one to run little items likw a
small TV or such.
 After that you can judge if you need more PV panels or battery backup etc.
 One of the good things about solar power is that you can build a system
slowly untill you get where you want to be.
 Joe

 Ira Serkes wrote:

This gets into "PV system sizing". There are various websites that
will help you out as well as any good PV salesperson. It's been
covered in this newsgroup numerous times so a good google search
should find many references.

The general idea is to work backwards from what you want to power.
In your case, a fridge, some lights, etc. All of these vary, but
for example my fridge uses 1.3 kWh/day, some 14W CF lights running
a few hours a day, say .25 kWh/day, everything else .1 kWh/day
for a total of 1.65 kWh/day. Batteries are around 80% efficient
and I'll want 5 days of storage in case of bad weather and I'll
only want to discharge them a max of 80% so I'll need something
like (1.65kWh /.8 /.8 * 5) 13 kWh. Let's say it's a 12V system
for convenience that means (13,000 Wh / 12V) 1083 Ah. A typical
6V golf cart battery runs around 220 Ah. I would need 10 in
series-parallel or roughly two for each day of cloudy weather.
Larger batteries would probably work better. The alternative
would be to forget running the fridge in cloudy weather and
just buy enough batteries to run for one or two days.

How much PV would I need? Well, PVs produce as little as 80%
of their STC rating in hot weather and they would have to have
enough to recharge the batteries (80% efficient themselves) and
we might have as little as 3 'sun-hours' of light during the
winter so say, (1.65 kWh/day / .8 / .8 / 3) .860 kW or 860 W.
Call it 900W at $8/W installed that would cost $7200.

Then again, if we drop the fridge from the list then I'd only
need .35 kWh/day which works out to (.35 /.8 /.8 *5) 2.75 kWh
of batteries or (2,750 / 12) 230 Ah which is very close to
220 Ah and I could get away with just two golf cart batteries
in series. The PV's might cost ( 350 / .8 / .8 / 3 * 8) $1500
and maybe less if I buy seconds and mount them myself.


Generators are much less expensive than PV, especially if only
needed for the 100 years earthquakes. Most people have no problem
keeping propane on their lot for BBQs, having natural gas piped
in or storing gasoline in their cars gas tank.

Just the point out the obvious, PV panels only work when the sun
is shining. Everything has it's good and bad points.

Anthony