Solar

Considering Solar

A solar setup may be used to do a couple of things. It can eliminate the need to be connected to the power grid or it can be used to suppliment the power drawn from the power grid and lower the cost. In all cases it might have batteries which can supply some power in the event there is no other source.

The solar system can supply power at various voltages. Examples might be 12 volts DC, such as most vehicles use, 120 volts AC such as most appliances in your house might use or even 240 volts which might be used for a dryer, electric water heater or stove. I am referencing U.S. voltages as European ones are different. In the U.S., we generally have two 120 volt AC circuits where the phase of the power is opposite. If the need is only to power various 120 volt loads, there is no need for a split (dual) phase system. That can reduce cost considerably. However if there is a need for the 240 volt circuits in the U.S. a split (dual) phase system is necessary. In U.S. circuit breker boxes there are two separate input lines from the utility. Between eaither of them and ground is 120 volts, but across the two hot lines there is 240 volts. Our breaker boxes have those two 120 volt lines on opposite sides of the box. To get 240 volts, a dual breaker is used to connect to both 120 volt lines.

So deciding just what you wish to accomplish with a system will help determine the costs.

A major cost of installation is of course having people on your roof drilling holes. More ont hat later.

Solar Info

I already have 20 solar panels totaling about 2kw capacity.

I ordered a split phase controller and 2ea 48 volt 100 Ah capacity, giving about 200Ah battery capacity.

I will receive power for now from the solar and the grid as I do not have enough capacity to go full off grid.

My current grid usage is about $240 a month and they are switching me to TOD rates.

For grid power I will pay per Kwh:

25.5 cents from 9am to 5pm
59.9 cents from 5pm to 9pm
52.9 cents from 9pm to 9am

These rates reflect the utility being able to charge less during the day when the sun is out. The more people they can convert over to use power when the sun shines, the less storage they need.

One scenario is to use solar to charge the batteries and not use any grid power during the day and to use battery capacity until 9pm. Thus no charge from the utility except from maybe 9pm to 9am.

However, based upon my current costs, I pay

$ 46.16 from 9am to 5pm
$ 55.83 from 5pm to 9pm
$124.85 from 9pm to 9am

So in my initial calculations I would save about $102 by just paying for power over night.
I could save a bit more by making sure I have battery capacity from 9pm to 9am and that saves me about $25 more a month.

I have not taken into consideration use of the dryer or stove, which I can use with solar or use during the day from the utility when rates are low.

So I will have to see just how much power I do generate and them make some decisions. They might include adding more battery capacity and/or adding more efficient solar cells. The better cells just allow me to use higher power during daylight and also to ensure my batteries are fully charged. It does nothing to extend my capacity over night, that is what the batteries do.

So costs:

I already have the 2kw worth of solar cells having bought them a decade ago and not used them yet.
The controller was about $1400 and the two batteries were about $2600 total, then add $1,000 for shipping. So total is about $5,000.

If I could completely eliminate the grid, I could pay the system off in a year and a half. As you can probably guess, that won’t happen based upon efficiencies and so on. BY just my calculations above of saving perhaps 1/2 the current grid cost, the break-even is about 4 and a half years.

That is still quite low compared to buying a system through some kind of lease or having professional installers drill holes in my roof. You see, I have a farm and can ‘prop’ the panels up in the side yard. Actually I will mount them above ground and ensure that I can swap out the panels for bigger ones later. A professionally purchased and installed system might have a payback period of 7 to 10 years or more.

So how difficult is it to set up your own system?

I will mount the panels and point them in the direction they need to be. I’ll run some wire in a conduit to where the electric breaker box is. I will then mount my solar converter to the wall and hook up the two bateries. I’ll add a master disconnect switch which allows someone to press a single obvious button to shut down the solar system in an emergency. I will decide which home circuits I want to always run off solar if necessary and those existing wire connections will be routed through a transfer switch. This switch allows me to have these circuits run off my solar system most of the time, but if I run out of battery or the controller breaks, I just throw a switch and the items in the house go back to the utility grid power. The controller itself can switch its input from the solar panels to the grid if there is no battery or sunlight. I want to be able to also be able to just keep some circuits switched they way I want. I also will have to decide is I want to keep the range and dryer on the grid because of their draw, they would use lots of battery capacity, but I also could use them during daylight as long as my batteries will be charged before sunset.

Yes, I could just add more cells and more batteries and be completely off grid, but that is an extra expense. Keep in mind that the utility is still going to charge me some money every month as a standby charge whether I use power or not, sort of like insurance that there will be power available if I need to buy some. My Sisters have a cottage and are completely off grid for electric. Although they are running just LED lights and a few appliances, there have been a couple days when their power went off just before sunrise. So for them one extra battery would probably solve that. They also have a washing machine but no dryer or electric oven/stove. The use a propane cooktop and that seems to work fine for their needs. The fridge with freezer was their biggest need so they could stop buying ice daily for their food.

So I have looked at my weather station data and determined that late afternoons here have diminished sunlight, so I will adjust the panels to favor the morning sun. Also I have a couple of actuators which will allow me to adjust the panels to catch the sun at the best angle during the seasons. Otherwise I would experience a 15% reduction in sunlight capturing. Yes, there are systems and setups where you can automatically track the sun during the day and during the seasons, but the expense hardly seems worth the cost.