2022.10.08 N0ZYC solar power presentation notes


HOW DOES SOLAR WORK
- different kinds of "solar power", including direct water and air heating
- similar to a diode, PN junction, exposed to light moves electrons across junction
- voltage is similar, 1/2v, but current can be high depending on area of junction (size of cell)
- combine cells in series for higher voltage, parallel for higher current
- voltage isn't regulaged, requires a controller (usually bucking down)
- typical consumer grade panels are about 22% efficient (1000 w/sq meter testing)
- shaded junctions can produce heat if reverse biased, diodes used to isolate panels that aren't producing

PANELS
- rigid or flexible - rigid better suited for permanent installation, protection from elements
- also small solar "wallets", not much power but good for charging a phone or power bank
- home panels usually string 32-120 cells in series for 16-72 VDC at around 5 amps
- most new home installations use micro inverters for each panel, may generate EMI
- panel angle is important, 45deg in the summer, 60deg in the winter, or leave it alone for less power
- many fraudulent panel values

CONTROLLER
- DC controllers trade voltage for current, usually includes a large 120v inverter
- if using micro inverters, regulates panel frequency
- both designs either charge batteries, sell back to the utility, or both (discuss tradeoffs)
- DC panels need to keep voltage within limit of controller, discuss parallel/series
- many grid-only systems that use micro inverters will shut down if line power is lost
- home controllers have a remote that's a bit like your furnace's thermostat
- always connect the load to the load port so the controller can disconnect the load to prevent deep discharge

TRANSMISSION LINES
- DC is current/voltage tradeoff, for power loss, AC is simpler
- connections and wire need to be weatherproof (water, ice, and UV)
- DC and AC are both high voltage hazard - home panel feeds can exceed 70 volts DC, and may be as uch as 300-0v
- MC4 connectors are industry standard

HOME USE
- average payback is 8-15 years
- SLA batteries need replacement every 10 years
- offset electric bill by getting credit for power
- usually requires professional installation of transfer switch and home controller
- not every utility is willing to buy back power or will give you a fair price
- some vendors sell you solar cheap but then charge you for your power for like 20 years
- having a power charge in force makes it hard to sell your house
- HOA may not allow you to install it
- home controllers can be over 1,000 watts, though they're more efficient with 24 volt storage and systems
- majority of home solar sellers are scammers, get multiple quotes, don't believe in drems and miracles
- don't expect huge credits or lots of negative bills

FIELD DAY USE
- portability is important, flexible panels are much more convenient
- ability to angle the panels reduces portability, easier to just lay them down
- make sure your wires aren't a trip hazard
- EMI from the solar controller can be a problem, make sure you can filter it
- the goal is to keep the batteries fully charged for overnight use, or at least not die on saturday
- typical flexible panel is 36 cells, 100 watts (rated), 75 watts (actual)
- the largest of the small controllers top out around 300 watts (four 100w panels)
- 24v option available on the larger controllers, requires users to have dc-dc converters
	
PERSONAL USE
- hiking, camping, RV power, sailing
- charging a battery bank lets you time-shift your solar charging
- cannot just attach a panel directly to a car battery, small controllers are very cheap ($15)

ACCESSORIES
- inverter - modified sine wave and true sine wave (pros and cons)
- 12v LED lights are very efficient, like RV lights - also 12v desk lamps are available
- lithium batteries are lighter but more expensive, voltage is higher requiring compatible controller,
  cannot parallel with lead acid