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"The sunlight that fell on roads in the United States last year contained roughly as much energy as all the fossil fuels consumed in the world. Photovoltaic cells, commonly called solar cells, are an extremely attractive energy option.
Easily integrated onto roofs, walls and windows, they have no moving parts to break. Solar cells produce no acid rain, no greenhouse gases, no radioactive waste, no bomb-grade materials. Its energy can be stored in a battery, fed into an electrical grid, or used to split water into hydrogen and oxygen. It offers the promise of abundant, convenient power otherwise  constrained by the threats of climate change."  
Denis Hayes, Environmentalism Essay 2005

Whether you are building a solar home or installing solar collectors.

Shade from trees change month to month. And a panel facing up collects more in the summer, for pool heating or air conditioning.

But a vertical panel collects more in the winter for heating or lighting. An angle equal to the latitude is good for year round…here about 38 degrees.

Sunlight as a Resource

Sun tracking can improve your summer energy collection by 45% and your winter, by 25%. You it can improve your yearly average by 35%. However compare the cost with 35% more low cost solar panels with no moving parts.

Solar Energy in Comparison

Germany, with 5X the Solar Generation, has less sunlight than any part of the Lower 48 states except Seattle. It is a decision Kansas as a state can make.

Solar Energy

Solar Thermal

Solar Electricity

From the ground they look alike, dark color to absorb the sunlight and an aluminum frame because they both live for decades outside
But solar thermal is more efficient, capturing about 50% of the light hitting it. It can heat water or air. We haven’t found an efficient way to air condition with it.
Solar electricity, or photovoltaics (PV) tops out at about 20% efficiency. But electricity can be used for everything we do: from cooling and heating, computing and lighting to transportation.

Solar Electricity or "PV 101" is what we’ll be discussing in this class.

Types of PV Panels

Amorphous Silicone           Crystalline

Monocrystalline ------- Polycrystalline

Solar Electricity is no longer the solar you remember

To carry that the current to light a normal 60 watt lightbulb, we had to use very fat wire…lighting that bulb took the same wire as a normal electric water heater….10 guage.
With the exceptions of water pumps, we needed big batteries to store the electricity. Normal electricians didn’t know this craft. The only appliances which worked were ones we bought from auto or RV stores. These were all of poorer quality than ones everyone else could buy at Walmart for half the price.

We needed normal AC household power.

Lead Acid Battery Banks

They are still the cheapest way to store energy in independent systems or provide backup to Grid-tied Systems.
Battery "Rules":
  • Only in a house you will consistently occupy. The most difficult systems are for ones empty for months.
  • If the battery is too small to give you a hernia, then it is probably not "deep cycle"
  • Only one or a max of two parallel strings
  • High voltage to both minimize resistance and have high capacity, feeding a 48V inverter
  • They all prefer to operate in the top 20% of their capacity and you have to factor in cold…and heat.
  • Far preferable if you have grid power to routinely equalize the battery bank
  • Always underestimate battery life
  • Even with decades of battery experience, battery electrochemistry is a fuzzy science.

Alternating Current (AC) Waveform

It is important to understand this wave form because our wave passes zero volts 60 times/sec. So an electrical arch extinguishes itself with each crossing. With Direct Current (DC) an arch will sustain itself until the current stops. This makes DC currents much more dangerous and destructive once an arch starts. For example, a standard wall switches last about 2 weeks with 12VDC.
The hardware which changes DC to AC electricity is called an Inverter. By the late 1990’s we had inverters which produced power equal to the quality of utility electricity…but still battery based.

Solar Electric Systems. (Photovoltaics circa 1990):

--- Independent system ---

Until 2001, there were still no connection to the powerlines.Homes had inverters which generated cleaner and more consistent power than most got from the powerlines. But because the inverter’s frequency generator was on its own, there was no reason for it to synchronize with the lines. Often, people had red outlet covers for their own power and black covers for grid electricity. If for some reason they got crossed, the powerlines would always smoke the inverter.
So every household still had a rather sizable battery bank with all of its foibles, sulfur smell and maintenance.
Batteries would be the biggest investment over the life of the system, and power’s trip to the battery and back lost 20% efficiency.

Batteryless Grid Tied PV

However, when the lines are down, there is no storage. So you need to resort to the same measures as all your neighbors. But there is no danger to utility linemen from your system. Inverters shut down.