Energy and Environment Week 10

solar

Solar current capacity

Accounts for 6.9% of global electricity generation (in 2024; up from 5.5% in 2023)

• 428 GW solar capacity added globally in 2023

• Total installed solar capacity (world): 1419 GW

Far more added than other sources; solar has seen a large reduction in cost

Solar sources

The best sources of solar are very sunny places, Like Australia

Concentrating solar power

A tower with a point and many surrounding mirrors that bounce sunlight back to said point

Solar water heating

A passive source of solar installed on rooftops, where sunrays are used to heat water

Learning curve components

1. R and D (research development)

2. Learning by doing

3. Economies of scale

4. Learning by waiting/spillover effects from other tech

Not applicable to fossil fuels

Wright’s Law

Technologies that follow Wright’s Law get cheaper at a consistent rate, as the cumulative production of that technology increases

Semiconductor

Conducts electricity when energy is provided. Absorbs photons (sun’s energy) & transfers to electrons. Electrons flow through semiconductor as electrical current

Silicon layers in solar cell

sunlight hits the conductor and generates:

• N type Si: extra electrons

• P type Si: extra spaces (holes) to receive electrons

P-N junction

• The electric potential barrier between the two semiconductors of a solar cell

• Creates low resistance path for excited electrons to flow through

• “Loose” electrons flow from the rich end to the poor one creating a direct current (DC)

• This is called the photovoltaic effect and explains why solar cells are actually PV cells

Solar manufacturing process

image

Dominant tech for PV modules

Crystalline polysilicon (98%)

Thin-film cadmium-tellurium (CdTe) is more efficient alternative but does not last as long

PURPA

Dominant utilities must purchase power from renewable producers if cost is at or below utility’s avoided cost. Rates and terms are set by MT public service commission

Net Metering

Homes and businesses can connect DERs (renewables) to the electric grid and get credit on their power bill for excess production. Inverters convert direct current energy to alternating current energy

leftover credits each year are forfeited to the grid

Solar power life cycle

CO2 production only included in transport and making of materials, and depend on location. Panels have a ~25 yr lifespan, and energy payback time is varied

EPBT (energy payback time)

time required for a PV system to generate the same amount of energy as needed for its entire life cycle

Strategies to remove adverse impacts of solar land intensity

• rooftop solar

• placement in already disturbed areas

• agrivoltaics

• floating solar photovoltaics (behind a dam)