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Solar - Grid-Tie or Off-Grid?
Bob Bruninga, WB4APR
If you have no access to the GRID, you have no choice, you have to go ... off-grid!
But if you have the grid and are considering going off-grid or using batteries for any reason,
please review this page and also join our discussion group.
Solar Presentation given at the 2011 TAPR/AMSAT dinner at Dayton.
in the USA.
net energy flows.
Staying on-grid can give you nearly triple the power for about the same cost and
avoid battery maintenance for the rest of your life.
We all want to take advantage of the
tremendous drop in solar panel cost and the significant economic advantage of owning our
own power station (as shown to the right).
This chart shows the 12:1 drop in panel prices over the last decades and 2:1 drop just
last year.
The chart also shows the world exponential growth in production of solar PV panels.
The 2010 value of 14,000 MW is not even shown full scale on this chart!
Costs are so low you can now buy a
Thats $3.60 per watt.
Installation of solar PV systems will almost double to
And DIY'ers with a master electrician friend can install Solar panels for as low as 75 cents per watt
in 2015! almost 5 times less!
Here are some other web pages related to my experiences with home solar power:
on Federal Installations
Presentation (April 2011 at TCF)
Do not think the grid is your enemy!
It is your economic lifesaver!
OFF-GRID (with Battery storage) Makes No Economic Sense (if you currently have Grid access)!
The reason is simple.
Modern grid-tie (net-metered) solar systems get 100% efficient and nearly unlimited
storage in the grid and require virtually no maintenance for life.
On the other hand,
Off-grid throws away 30% or more of
your solar power in charging/discharging losses as shown to the right.
Further, battery systems
throw away another 50% of your annual
incoming solar power because the battery can't save the excess power in summer for use
in the winter when you need it.
Finally, the lower production in the winter
causes you to give up half your electrical lifestyle for a few months.
Why does it sound like I am anti-batteries?. . .
Because I always thought you had to have batteries
as part of any solar system, and there was simply no way I could make the numbers work out
for home-solar to be economical (with-batteries).
So I wasted several years with this
totally incorrect assumption and am now getting into solar a few years later than when it
became not only practical, but cost effective with grid-tie.
I want to save you from making
the wrong assumption too.
Forget batteries for Solar storage! (if you have grid access)....
Batteries (if you want to buy them) are only for the 0.05% of the time the grid might be out.
But like any power outage, a small generator or your car and inverter as
described in sections below can much more cost-effectively meet your 0.5% needs.
LESSON #1, Losses: Putting
energy in a battery throws away 30% to 40% right off
the top in charge and discharge inefficiencies as shown above.
If you have access to the grid,
it makes no economical sense to give that up!
Energy storage in the grid is 100% efficient
and virtually unlimited whereas storing energy in batteries is limited and not only throws away 30%
of your energy, but also:
LESSON #2, Limited Capacity: Off-grid also throws away all excess solar power
once your batteries are fully
charged on a good summer day as shown to the right.
You either have to waste the excess summer
energy or find resourceful seasonal uses.
In any case, you then suffer a 50% energy
life-style change in the winter.
With a battery system there is simply no way to
save excess summer energy for winter use.
Typically a battery system is sized to
hold a few days energy on the worst solar day of the year (December).
But the solar power
available then is about 1/2 of what you will get in the summer per day.
LESSON #3, Wasted Excess: Even if you invest lots of money in a double sized battery
to assure you can capture all the excess solar on a long summer day,
you and your family must find a way to use all that extra power that night
in order to have battery room for the next day's summer flood of excess solar power.
The result is you generally waste excess summer solar power.
For comparison, it would take
3240 batteries to save that excess (double) summer solar power for the winter when you need it.
(Actually, there is a perfect system for long term energy storage... and it is called THE GRID)...
LESSON #4, Grid-Tie Capacity: With grid tie, you basically have an infinite capacity
storage system that
can save summer excess power and give it back to you in the winter or cloudy days with 100%
efficiency.
Actually, it is not infinite, it is basically equal to your TOTAL annual
energy usage because the power companies expect you to not bank up excess power longer than
There are two ways the Utility deals with annual over production.
if your meter shows a net negative after a full year, the utility will re-establish that
as your new annual starting point and cancels any overproduction credit.
Some utilities
will pay you for the excess but not at the retail rate, but at the 2 cent wholesale rate...
Bottom line is to simply not OVERBUILD your array
more than you typically use in a year (unless you simply want to help your fellow man).
LESSON #5, Battery Maintenance and Replacement: There is no battery maintenance with Grid-Tie.
With batteries, you are burdened
with continuous maintenace and periodic battery replacement for the rest of your life!
LESSON #6, Reliability: It is very hard to justify a whole-house battery backup for very rare
grid-outages.
In most places the grid is up
99.9% of the time and only down maybe 0.1% of the time.
The economics of grid solar win-hands-down
99.9% of the time, and for the 0.1% of the time the grid is down, economics suggest that investing
in a $500 generator and 5 gallons of gas is by far the more cost effective approach.
You can even
avoid that with a $100 investment in a 1 kW 12vDC to 115 VAC inverter for your car, and plug your
emergency needs (refrigerator, lights, etc) into that.
Do not be sold a $6,000 battery backup addition to your economical grid-tie solar system
when there is a $100 solution! See additional sections below.
LESSON #7, Siting Inflexibility: For battery systems, there is only one optimum
solar panel orientation, that is,
facing due south at an angle equal to your latitude.
This is the only way to meet your minimum
power needs in the winter.
Any off-angle reduces your winter life-style.
Being 30 degrees
off reduces your power by COS(30) or 13%.
But with Grid-tie, the only thing that matters is
Annual-Average power.
In the winter you can draw as much power you need from the excess that you
stored in the summer.
estimate to the right for the 180 South array tilted to 39
degrees for Maryland.
Now, since only annual average counts, it turns out that for any angle off
from due south, there is a different sun angle and time of year when that array will produce MORE
than a due south arrray and this makes up for it.
The annual power from an array to the Southeast
(150 degrees shown to the right) or one to the southwest (210 degrees) will only be down by
about 3% (not the 13% for
an off-grid system).
ALso, you can change the TILT angle by as much as 20 degrees (also shown
in this table) and only loose about 1% more.
LESSON #8, SREC's: With battery systems you do not get paid annual
Solar Renewable Energy Credits.
These credits in Maryland amount to a $300 per year cash
payment for each installed KW of grid-tied solar power.
For an 8 kW system, this is a
$2400 annual cash payment simply for being part of your state's solar energy system.
Even if you produce no net excess power you still had to pay $10/ month for your
on-grid account.
But this SREC income makes up for your billing costs by 20 to one!
This year, SREC's in NJ were $600/kw making for nearly a $4800 income per year and
reducing system payback time to 4 years or so!!!
LESSON #9 No Choice: Off grid is for when you have no choice: and must generate and store your own power...
or it is cost prohibitive to run the grid to your house (now that most utilities pass that
cost directly to the user...)...
In those cases, Solar power with Battery storage is the
only way to go!
It is great.
(But so much better if you have the grid!)
If you do still choose to go off grid, recognize you will be paying a HUGE penalty:
Batteries waste 30 to 40% of your expensive solar power in charging inefficiencies
Off grid users have to throw away or waste lots of excess summer power (more than half their average power!)...
Batteries cannot store the 50% summer excess for use in the winter when you have 50% less solar available.
With off-grid, plan on a winter lifestyle change for living with HALF your solar average!
Plan on battery maintenance the rest of your life...
Plan on replacing the batteries every 5 years or so for the rest of your life.
Your array must face due south at the correct angle (unlike GridTie)
You still need a backup generator for long strings of cloudy days (And gas just keeps going up ==>)!
AMAZING ROOF ANGLES:
Grid-Tie solar is a huge paradigm shift in conventional thinking
about solar power.
South is dead.
With grid tie, there is hardly any real
requirement at most latitudes to worry about exact roof facing.
The number-1 consideration
is Trees and shading!
Those have far more impact than roof facing.
It turns out that having
an EAST/WEST facing house can produce more grid-tie power than a south facing one!.
In the image above left, is the the classic south facing roof.
Yes, it produces the maximum power as one would expect at a
40 degree tilt for a 40 degree latitude house.
But for the more typical roof tilt of say
20 degrees, the penalty to the grid-tie homeowner is only 2%.
Further, if you rotate
the house to the southeast, only 5% energy is lost.
Even if facing due East, the 20 degree
grid-tie roof can still produce 85% of the total annual energy as the ideal Southern array.
Whole Roof! But wait, there is more!
If EAST can produce 85% of what South can do, then covering the
WEST roof can produce 170% of what South can do.
Amazing...
But wait, there's more...
Lets look at the Southeast facing roof.
The sun sets in the North West in the summer
and so lets double the array on to the Northwest roof... Wow, almost the same output
as the East-West array... OK, why not try the NORTH facing roof as shown on the right.
Yes, this northern roof will not generate any power during the winter solstice, but all the rest
of the year and especially during the summer, it will produce 60% of what the South
face will produce.
If your southern roof is full and you need more solar, then do not
overlook the 60% imporvment
you can get by putting solar panels on the North side!
Emergency Backup Power:
And please think through the cost of whole-house backup
batteires considering the 0.1% of the time when
the grid goes out and you need backup power.
For power backup in the rare blackout a few hours every year
or the bad day or so every decade or so, simply use a small generator or
your car generator and an inverter.
See some of this on
Grid-out 250 VDC Backup Power: Just because the grid goes out and the grid-tie inverter safely
shuts down to protect linemen, your array still produces electricity (DC), you just need to figuire a way
to use it.
The key, is to realize that almost all modern power systems use switching regulators and
high frequency power conditioning.
This means that most of them will run directly on 250 to 330 VDC
just as easy as they will run on 100 to 240 VAC beacuse internally, the first stage is simply a DC
rectifier.
All voltage conversion and regulation is done from high voltage DC.
So instead of wiring
your grid-tie array for 500 VDC to minimize wire loss, wire them in series parallel to about 250 to 330
VDC so that you can use this power directly if needed.
Just about any system that has a nameplate
showing it is good for 100 to 240 VAC will work on 150 to 330 VDC too!
And almost all modern
electronic systems come that way!
But most appliances and lights are a problem.
You CANNOT wire
two CFL bulbs in series to equal 250 VDC, they are unstable and one will take all the voltage and burn
out instantly.
But you can series two incandescents of the same wattage, or you can special order special
220 volt CFL bulbs normaly sold in Europe.
But you will pay 10 times their value.
I'm looking
for surplus LED christmas light strings!
Large LED bulbs are ideal beacuse they run on 100 to 250
volts AC or DC but cost a king's ransom ($50 each). See the diagram below:
NET METERING: Of course, all the benefits of grid-tie solar depends on having NET METERING in
your area.
Meaning that all energy you put into the grid you can get back out for free.
Net Metering is the case in most energy conscious states.
The white ones to the right
apparently are the backwards ones.
Eventually they will wake up to the benefit for all.
All the world is going solar.
If your backwards county is not moving in that direction, get involved
and get them motivated.
It is a win-win for both the homeowner AND
the utility company, so there is no chance Net-Metering will ever go away.
Off-grid battery systems are ideal for small remote communications and electronic systems on mountain
tops or remote areas where the load is constant year-round (and it is the only possible solution).
But it makes no economic sense
whatsoever in a place where there is access to the grid.
Keep your grid! (if you have it).
Yes, you will have a $10/month metering fee even if you use zero
net power, but not only is that a trivial cost to pay to gain more than TWICE the power from your SOLAR
investment and to avoid messing with batteries for the rest of your
life and replacing them every 5 years.
But you will get PAID an annual
Solar Renewable Energy Credit from the power company that will more than make up for
the metering charge!
For each 1 kW of solar panels, you get an annual payment of $200 to $300
that much more than makes up for your monthly meter charge.
For my 8 kW system, that is $1600 to $2400 a year!
Plus you are HELPING your community!
Grid-Tie energy economics: Here is why the (clear thinking) utilities love grid-tie.
produce an excess 1 kW in the summer back into the grid, it really goes no farther back into the grid
than the nearest 1kW load (your neighbor!).
Now your power company still gets to charge your neighbor
for the 1kw, but does not now have to generate 2kW worth of electricity at the generator to make up
for the distribution losses.
And in avoiding generating 2 kW of power, they save more than 4 kW
energy equivalent in coal that they can save for later.
Often times, the utility might have to pay
10 to 20 times the normal rate of electricity from peaking-plants to meet peak demand.
Grid-tie solar in that case is worth 10 to 20 times its value!
You win, you pushed your meter backwards 1 kW
Your neighbor wins (he gets the 1 kW at standard rates)
The power company wins (they don't have to burn the 4kw of coal)
The power company also does not have to buy that 1kW at 10 to 20 times the cost from a neighbor utility
You get paid
for your system
The environment wins.
The coal was not burned.
PROBLEMATIC CASE WITH RURAL COOPS: Someone told me their coop has a basic $50 monthly fee
just for grid-access even if you use no net energy.
In the old days, this made sense.
Everyone has to pay for the basic infrastructure.
But with grid-tie, everyone wins.
The consumer wins
by getting good return on his solar investment, the coop wins because they get distributed power from
their solar customers IN the rural area where it is used, and it avoids burning twice as much primary
energy (coal) to deliver the same power to the loads.
It also saves them on added distribution
capacity and finally, it avoids them having to purchase PEAK electric rates since solar is producing
the most when everyone else is running their Air conditioners.
In effect, coops should be enthusiastic about grid-tie since it is a significant benefit to them as
well as their customers.
On the other hand, if coops do not wake up and realize that
their preditory pricing disincentivizes solar, they will end up forcing
their customers off-grid leaving them holding a huge infrastructure
with less and less paying customers to support it.
If you are in one of these backward-thinking coop
areas, write them, your county, your state, and your congressmen.
Educate them.
Home Owner Associations? Regarding prohibitive covenants, HOA's in Virginia in existance before
1 July 2008 may maintain their prohibition against solar panels. "Timehourse" reports it takes an 80%
HOA vote to reverse this.
Reference 67-701 of the Virginia Code,
Section C.
Pollution to Produce Solar?
The final argument by the nay-sayers is that it takes coal
burning electricity to make the solar panels. True, but that applies to everything we do
on the planet in our jobs and manufacturiing.
If Coal electricity is used to produce a panel, then
the emissions to manufacture are break-even with the clean energy produced in 1 to 3 years.
For a service life of 30 years, this environmental benefit is 10 to 30 times the environmental cost.
If the MFR's weren't making solar panels, would you rather their factories be making more
big-screen TV's and hot tubs and still polluting
in the process?
Plus this only goes up as more and more of our electrical power comes from solar.
SHACK POWER?.
I share the above with you, because my own backward thinking about batteries
caused me to avoid the cost of solar for years, when in fact, the only thing that made the
system uneconomical was the batteries and a lack of understanding of the benefits of Grid-tie
(if you have it).
However, like any Ham, it is also prudent to have a small solar backup and battery for
your HAM Shack communications needs as shown below.
In this case, simply adding one of the small micro-grid-tie
inverters to your shack will allow you to not waste your solar power once your shack battery is
The micro-grid-tie can provide about 250 watts of AC current to your permanent shack loads
to lower the consumption of power from the grid when the sun is shining.
For one 200 Watt panel,
these nickel's per day of excess power will add up to $30 or more a year in saved energy.
HALVE YOUR GRID-TIE INVERTER INVESTMENT:
If you are really scraping pennies together on your
solar system and have a partially shaded lot that does not have enough room for a full set of solar
panels, you might consider pointing half of them southeast and half of them southwest.
intitially this means you only get about half the power from all your panels, you are actually getting
that half power for almost twice as long during the day.
See the image below:
As shown above left, in the summer, the sun rises in the NE and sets in the NW and a southern facing panel
actually does not get any of the first and last hours of sun per day.
But if you split half of your panels
SE and SW, you can get more sun for longer.
An advantage of this approach is that you only need about 70%
of the grid-tie inverter capacity, because you spread out the power over time.
You can get buy with investing in only half the total inverter cost if you have some shadowing that blocks
enough of the full sun on both panels slightly before and afternoon to the diret south.
A good candidate for this approach is someone without a good low southern horizon, but that does have
good low horizon to the SE and SW.
Such a site is going to produce little power in the winter anyway
because of the low horizon blockage.
Splitting the panels might be a net gain (with half the cost for
inverters)...
BUT IS GRID-TIE-FOR YOU?: Now, grid-tie is great but there are a few other points that need to be
And that is, there are about 4 ways to hook up a grid-tie system.
I will address the issues with
Contractor Grid-Tie:
This is the full-up whole house method that has killowatts of solar
panels, installed by licensed contractors and master electrician and has a NET-Metering account with the
This is the common way to go for the homeowner and is the assumption made in all of the
above Grid-Tie benefits.
Mechanical Meter Grid-Tie:
Many MECHANICAL meters are by definition a net-metering device
because if you push energy through them backwards, the numbers count down instead of up. (unless it has
a mechanical ratched that will not let the numbers go backwards.
Do not make the mistake I did
wtih my ELECTRONIC meter.
I activated my grid tie for a month just to test how it worked
(before alerting the company to configure my electronic meter for net-metering).
Yes, I could visiually see the
meter disk running backwards, but I didn't hang around long enough to watch what the ELECTRONIC display
It counted FORWARD.
When I got my electric bill, I paid double.
for all the electricity we used PLUS the electricity we SUPPLIED!
Own House Grid-Tie: This is for the experimenter that has maybe 200 watts or so of
solar panels and he wants to feed that into his 60 Hz AC house system to more or less equal the sum
of all those insidious chargers and wall-warts and other constant loads in his house.
He is not really
backfeeding the grid but trying to drive his home's insidious load on sunny days to zero.
There are many
imported 250 Watt microinverters for this purpose (shown to right).
One of these is not really
backfeeding the grid per se, as long as its output does not exceed his insidious load.
IN this case his meter never runs backwards (just slower by the amount he is producing)
and so the type of metering is not an issue.
But if he overfeeds, his electronic non-net-meter will CHARGE him for
any excess he pushes backwards.
In any case, these GT inverters are safe, because they will
all shut down if the grid is lost.
Thus, they are not a shock hazard if the grid goes down.
Out0of-the-box-test:
I just got one of these and on my first test, with a pair of 12v batteries (24Vdc) the
inverter was drawing 4 amps (96 watts DC) and on the AC side, I was measuring almost 810 mA at 119 VAC
indicating almost 100% efficiency (my shunt resistor was 5% tolerance, so the inverter was at least
meeting its 95% efficiency spec.
At least there was no smoke.
Look at the drawing above on Halving your Grid-tie
Inverter Investment.
You can use that concept to double your savings while still keeping below
the backfeed ZERO threshold.
Say you have about 200 watts of insidious constant load in your house.
you do not want more than 200W of solar panels (at a time).
But you can still double your savings
by pointing one 200W panel East and another West so that only one is illuminated at a time.
This way you do not exceed the insidious load, but
you get to cancel the 200 watt load for twice as long.
The hard part is figuring out what your lowest daytime not-at-home load is
Tiny-Wind Generator: This is my use of a micro-grid-tie inverter.
I have a small 400 Watt
wind generator that hardly ever runs, but when it does, and its 24 volt battery is full, then
I want that excess power to go somewhere.
Since I already have a Net Meter account and three very
expensive 3 kW each high voltage solar grid-tie inverters,
I can plug in a small 500W micro-grid inverter (with 24 VDC input) and capture some
of that excess wind energy.
Anyway, just some thoughts.
Bob, WB4APR
You can see more about my spiritual awakening about solar on my other energy web page links near the
top of this page.
The rest of this page has not yet been edited out and is just some old stuff on other pages.
, And there is another page
See my nearly born-again
conversion to a Solar Junkie
in August 2009!
POLLUTING ALTERNATIVES:
If you look carefully in the photo at right,
you will see the smokestacks of
the 500 MegaWatt A.H. Wagner coal-fired generator plant just 4 miles down the creek.
By my calculations, just my home alone consumes about 10 MegaWattHours (MWH)
of electricity per year.
I hope to generate my own solar 10 MWH to eliminate completely
of the pollution from that plant which amounts to:
22,000 lbs of Carbon Dioxide
350 lbs of sulfur dioxide
1 ounce of Uranium and Thorium
.00004 ounce of Mercury
All of this pollution that I am responsible for is falling on the
nearby Chesapeake Bay and watershed and my creek.
Yet, I want to
eliminate my contribution to this pollution by
installing my 8 kW clean-solar system which will just about break even by producing my own
annual 10 MWH's of clean-renewable-energy.
So, at my own expense, I am offering to
clean up the Bay by having solar panels on my pier, but am blocked by an outdated and
short-sighted law of the Maryland Department of the Environment who are charged
with protecting not just the water under my pier, but the air above and the soil beneath.
Plan-B Solar-in-Yard: 21 Dec 2010 - So, after 9 months and $2000 of fees, the MDE's denial of panels on
piers still stands.
So I designed the panels to sit on the only sunny part of my lawn down
by the water.... Don't be fooled by the winter image above.
My roof is more than 50% shaded
throughout all times of the day and most months of the year.
submitted for a building permit in September 2010 only to be immediately
DISAPPROVED!
Maryland does not allow anything to be built within 100' of
the shoreline.
So, with additional fees, I applied for a Variance.
On 21 December 2010
I appeared before the Hearing Officer and presented my case.
Here are some of the materials I
Environmental Benefits of Solar:
The above two images show the pollution-elimmination impact of my solar project.
3'x5' panel eliminates about the same amount of pollutants in a year as about 8 mature
trees remove in a year.
This means my 42 panel array is equivalent to
the environmental benefits of about 300 trees compared to coal.
But even more telling is to look at not just the pollution impact of coal electricity,
but also the sheer magnitude of environmental distruction.
Unseen Impact of Coal Electricity:
In the image to the far right are 4 tons of coal which is about the energy equivalent of the
10 MHhrs of energy our house requires per year.
Not only do we energy-consuming-&-wasteful
Americans not see this tonnage, we also do not see the 80 tons of trees, topsoil, habitat
and dirt that has to be pushed off a mountain top in West Virginia and into the nearby
valleys and streams just to get to that coal.
This 80 tons of decimation of the environment
PER YEAR for my one house is shown in the near image to the right which shows four 20 ton freight
cars needed to move that debris.
The next image below right is just one of the hundreds
of mountains and habitat in West Virginia being destroyed for our coal energy addiction...
Folks, this approach to our environment IS NOT SUSTAINABLE!
Variance Issues: With the proponderance of benefits of my solar project
in my front yard, the County did agree that the varance was appropriate, but with one big
catch-22 provision.
They requested that there be the standard mitigation for any variance in the
100' foot critical area buffer.
This means that the disturbance in the
buffer area (690 square feet) must be offset with 3-to-1 or 2000 square feet of new
In otherwords, I can have the solar panels, but I have to plant so many
trees in compensation that my lawn becomes a forest and we are back to square-ONE,
that is, no solar access!
The Hearing Judge has 30 days to make a ruling.
In our favor!
Now the building permit has
been submitted and then we will probably have to do battle with their requiements for
disturbance mitigation.
We will see if sanity prevails.
SOLAR PRIUS:
My first alternative energy project was my
I built from a salvage Prius..
It had been totaled on the drivers side, but I just
beat it out with a sledge hammer and coverd the bashed-in door with the white sign!
This soon morphed into my
project to combine high power solar,
with thousands of watts of backup gasoline
driven generator power in the Prius for providing emergency
operating events such as the annual Amateur Radio Field Day or
Scouting events shown below.
PRIUS POWER: The Prius is a power station on wheels.
It has a 12 volt electrical system for normal
car accessories, and a 220 Volt 7 Amp-Hour Battery for propulsion assistance,
two 50 kW motor-generators, a 50 Kw DC/DC converter/inverter,
and a 76 Hp gas engine all
integrated into a seamless power system.
115 VAC Power: is provided by a 1200 Watt AC inverter running on
the car's 12 volt power system (shown in the right photo above).
This 1200 watts
drawn from teh car's 12 volt system is augmented by the
100 Amp DC/DC converter from the car's propulsion batteries and generators.
SOLAR-POWER: . Adding solar panels
to the Prius not only provides free energy to offset the cost of gas a few percent, but also to
provide an effective application for solar power in other places where you might need
The solar panels shown here can provide as much as 215 peak Watts of power good for
about 1.7 KWh of free electricity
when parked for 8 hours in Arizona sun. (unfortunately, only 800 Wh in Maryland Sun).
Solar Power portability gives peace-of-mind where there
is no gas or plug-in electricity available. .
When you can take solar power where you need it, then its value can be far greater
than 15 cents per KWH and is cheap at any price.
Just consuming it in the Prius is an equivalent
payback of 30 cents per KWH compared to the 15 cents at home. . Plus it reduces
dependency on foreign oil! .
A 1200 Watt AC inverter in the back (see photo above)
provides plenty of AC power to go.
Emergency Solar Power Trailer: I had a few extra low voltage solar panels
so I put them on the solar
trailer to the right.
It contains about 300 watts of solar panels plus a deep
cycle marine battery and
1200 Watt inverter.
The top wood section of the trailer folds over to
not only protect the solar panels during travel but to also hide them
out of sight when parked
or not in use.
When closed, the top wood section looks like an open top trailer
with about 6 inch sides.
The false bottom conceals the nested solar panels.
In addition, when open,
the bottom set of panels are also hinged to give access to the battery and inverter below.
this area provides hidden storage for extra power cords, cables and accessories.
220 VDC POWER CONNECTORS: . One of the first issues with distributing 220 VDC
power is finding a safe connector that is innexpensive and readily available yet,
cannot be confused with any other electrical connector.
. This connector must
be unique to prevent anyone from plugging in any non 220 VDC device. . The connector
we came up with was a standard two-prong power plug but with two
PREVENTION devices
to prevent inadvertant plugging in of other devices.
The connector is shown above right.
A standard two-prong socket is used, but without the usual 3rd ground pin.
blocks the use of any 3 wire 115 VAC power cord. . In addition, a 3/16ths inch
nylon protrusion is fixed to the center of this receptical inbetween the two prongs.
This blocks the use of any 2-wire 115 VAC devices. . To make a mating two
prong plug, a standard replacement plug is used but the center is drilled out to
pass this blocking pin as shown in the photo. . On the right, this center pin
protrudes into an unused, and isolated area of the hard plastic plug construction.
. These connectors cost under $2 each for both the plug and the receptical.
Lightweight Power Cords: .
Because of the much lower current demand at 220 VDC, a #18 zip cord can easily carry
plenty of power over hundreds of feet. . In the photo to the right, the original
25 feet of large orange extension cord were removed and about 120 feet of #18 lamp
cord will fit on this convenient spool system.
. The current carrying capacity of #18 is as high as 10 amps, but I limit mine by fuses
to only 5 Amps.
. Again, the outlets are blocked from
any inadvertant use by the uninformed by the dual protection-blocking system.
switching power supplies or other loads that can operate
on 220 VDC are provided with these matching plugs.
(YOUR MILEAGE MAY VARY!)...
Bottom line: . The time is now to go solar!
We cannot continue to send
billions of dollars a day overseas to buy polluting oil for our energy needs
when it is right there outside our door.
Also think in terms of your total
energy footprint and consider how to integrate your transpotrtation demands
into your own home solar system and energy needs.
Bob Bruninga, WB4APR,}