Page 80 - A Comprehensive Guide to Solar Energy Systems

Chapter 4 • Solar Power in the USA—Status and Outlook 75

producing, often causing oversupply. Cycling of power plants causes large thermal losses,
a slight increase in emissions, and the potential for mechanical failures, reducing plant
life. In October 2016, the Federal Energy regulatory Commission approved CAISO’s “flex-
ible ramping product” that increases the ramp rate, or speed, of power plants to start and
stop production. In this market mechanism, the ISO pays generators to remain off during
high periods of solar production to compensate for lost revenue. As such, CAISO shifts
costs to those necessitating flexibility [42].
Spotlight on Data-Driven Valuation: In addition to NrEl’s suite of modeling software,
the valuation of solar and grid modeling requires sophisticated analytical tools. One ex-
ample of such tools is Greenlink’s ATHENIA, which can generate hourly and daily gen-
eration scenarios of solar in regional service territories, quantify existing generation and
assess the potential for future growth. The software is designed for informing state and
city policymaking through determining the social, health, and environmental benefits of
distributed solar energy generation [43].
Other emerging modeling and forecasting techniques incorporate the use of stochastic
modeling and Unit Commitment and Economic Dispatch models based on General Alge-
braic modeling System (GAmS) [44]. These methodologies are able to incorporate numerous
variables to anticipate, among other issues, the financial value of solar to the grid and system
upgrade requirements. Ongoing r&D in this area involves system-specific analyses to iden-
tify the optimal combination of technology, grid infrastructure, and operational challenges
beyond 30% variable rE, the point at which significantly greater investment will be required.

4.4.3 System Upgrades

As PV comprises an increasing share of US generation, the physical infrastructure of
the grid will need to be upgraded. A partnership between the DOE and 13 National
laboratories, the Grid modernization laboratory Consortium is working to equip the
grid with the technology needed to meet the increase in clean energy and distributed
generation [45].
Concerns abound that increased renewable penetration will result in system inter-
ruptions. The US, however, would benefit from examining the experience of Denmark
and Germany, both of which experienced less power outages per recent years than
the US and have four and two times the percentage of renewable energy on their grid
(Fig. 4.25) [46].
Nonetheless the increased penetration of renewable energy will require transmission
system upgrades. large “utility-friendly” power plant technologies are being introduced
[47] but constraints in small systems remain; these include the need for bidirectional pow-
er flow, and inverter electronics that better synchronize with the grid. Bidirectional power
flow is required for grid-tie PV systems that export excess energy to the grid. Inverter elec-
tronics refer to PV inverter’s short circuit current capacity and ability to harmonize to the
frequency and voltage of the grid.