Grid-Connected Solar PV Systems

Grid-Connected Solar PV SystemsShawn Murphy

September 29, 2011

Shawn Murphy, PE • ENGR10 Guest Speaker

Solar Photovoltaics◦ Electricity Generation, the CEC and PUC◦ Silicon Solar Cell production◦ Technical challenges of grid-tied solar◦ Grid-tied issues◦ Permitting and Rebates◦ Net Metering◦ Design issues

Solar Engineering as a Career◦ General class recommendations◦ Training on solar PV

Outline


Conventional Energy Generation


There is no good way to store electricity Batteries Peak energy is more expensive and more

polluting Energy produced during high demand

periods is more valuable

Electricity Storage


California Energy Commission Founded early 70’s CEC goals

◦ Generate power using alternative means◦ Generate power during peak hours

Public Utilities Commission Regulate public utilities like PG&E, SCE and

SDG&E Tells utilities what they can charge for electricity Decoupled utility profits from electricity

generation

The CEC and the PUC


Similar process as semiconductor manufacturing. Conventional silicon still dominates market

Solar Photovoltaic Panels


Poly or multicrystalline Silicon

Monocrystalline Silicon


Much simpler than battery-based system. Grid serves as free, infinitely-large, no-

maintenance battery System sizing not as crucial Can be designed to maximize yearly annual

electricity generation. Does not have to be optimized for winter production.

Can operate at much higher voltages, saving power losses.

On-Grid Solar


CEC goals◦ Generate power during peak hours◦ Generate power using alternative means

Grid connected solar photovoltaic◦ Maximum generation during sunny summer days◦ Distributed generation◦ Uses existing spaces◦ Very quick deployment

Grid Connected Solar PV Meets the state’s goals


Power Quality Safety Connection to Existing Equipment

Technical Issues with Grid-Connection


How do you keep track of the power? How much do you pay for the power? How do you take into account when the

power is produced? How do you determine the rebate amount? How do you incentivize grid-connected solar

at the proper amount over time? How often do you read the meter? Who inspects the system?

Grid Connected Solar


One single meter that spins forward and backwards.

Meter can take into account time of use rates

Annual true-up Minimum monthly meter fee, $4 to $13,

charged by utility

Net Metering & Interconnection


Tax Credits and deductions◦ 30% FITC◦ MACRS depreciation◦ Various state tax breaks

Renewable Energy Credits State Rebates California Solar Initiative

◦ Declining schedule – based on expected performance

Rebates and Incentives


Must know how much a customer is paying for electricity

How do you compare one-time cost of a solar system versus the value of lower electricity bills in future years?

Engineering economics◦ Payback◦ Net Present Value◦ Internal Rate of Return

Economic EvaluationSolar Offsets Electricity Use


Engineering Economics Accounting Technical Writing Public Speaking Engineering Statistics Computer Drafting/ CAD

◦ Google Sketchup◦ Autocad◦ Solidworks◦ Pro-E

Recommended Classes


PG&E Energy Center Diablo Valley College Private classes

◦ Solar Living Institute◦ Solar Power International

Semicon – Intersolar SF July

More Solar resources

Grid-Connected Solar PV Systems

Documents

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