The Life Unwired with Ben Combee (unwiredben) wrote,
The Life Unwired with Ben Combee

Notes on Austin's Solar Policy

(This is from a talk I gave to the Trinity Social Justice class in May)

Austin's Solar Policy

- Austin Energy has committment to buying solar energy
- aiming for 35% renewable by 2020, 55% by 2025
- City of Austin wants to move to renewables
- Latitude means solar is fairly effective here in central Texas

How Does Solar Power Work

- solar cells are made of silicon with dopants that make them semiconductors
- photos from sunlight push electrons out of the cell, making a constant pressure or voltage
- this power is direct current -- it flows in one direction, and the current flow is dependent on
 how much sunlight hits the cells and the angle of the sunlight, and the temperature of the cells (hotter is worse)
- the power grid is alternating current with a constant voltage
- to adapt the energy, you use a device called an inverter that connects to the grid and the solar system,
  and transforms the solar power into grid power
- you often see the opposite form of these (in small) with power adapters that convert AC to DC for running digital devices like computers and cell phones
- Tesla just announced an inexpensive home-battery system that would let a homeowner save the solar power in DC form instead of feeding it into the grid

Cost of Solar

- Equipment and Installation
- Need sufficient unshaded roof or yard space to make it viable
- On my house, I have 14 200W panels, for a total system size of 2.8kW
- in practice, I never generate 2.8kW of power.  I've seen the system hit 2.6kW on really perfect days.
- On an awesome day, I'll generate around 18kWH of electricity.  For April, this generation really starts around 10am and goes through 6:30pm.  So, that's 8 1/2 hours of generation

- System cost about $15K to install
- 30% of those costs were returned in the form of Federal tax credits
- They estimate system costs as being 2.2K to 4.5K per kW
- I used to do my initial estimates

Austin Energy has two incentive programs for homeowners
- solar PV
  - Austin Energy rebates $1100/kW installed
  - they pay $0.113 / kWh, so I get a credit of about $2/day for my system at peak performance
  - max credit of $700ish year, but I've actually gotten more like $350 of credit a year
  - residental customers tend to pay $0.087 per kWH for first 500, then $0.134 for next 500
  - you still pay AE for the energy you use --
  - on a good month, it covers half to 2/3rds of our usage
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