Solar energy after dark – initiative in Arizona

New Arizona Policy Would Mandate Solar After Dark, Clean Technica December 30th, 2016 by Susan Kraemer A way to incentivize the use of clean energy like solar after dark — instead of gas peakers — to cover peak loads has been proposed in a white paper commissioned by Arizona’s Residential Utility Consumer Office, through a revision of state Renewable Energy Standards (RES).

Co-author Lon Huber, a Director with Strategen Consulting, was tasked with inventing a solution to the duck curve.

Huber told Utility Dive this week that his proposed Clean Peak Standard (CPS) should push developers to cover the need for generation at specific — peak — times.

“It adds more renewables, but it adds renewables when the system most needs capacity so it uses renewables to deal with system cost drivers and saves ratepayers money when electricity prices are highest.”

Under a Clean Peak Standard, during an identified peak demand period, a solar contract would have to deliver a percentage of its generation between certain — peak — hours.

A 25% CPS for example would mean that 25% of MWh generated during the identified peak demand period would have to be from “qualifying clean peak resources.” Currently, coal or gas peaker plants provide that peak generation.

So How Would Solar After Dark Work?

While so-called “spilled solar” at midday is already a concern, there are slim pickings so far in covering the evening peak with solar generation: battery storage or thermal solar.

The only solar projects capable of dispatching solar on demand at any time day or night, due to their thermal solar energy storage in the US are Crescent Dunes in Nevada and Solana in Arizona.

It is in Arizona, where the largest US dispatchable solar after dark project is sited, that this proposal is being considered. Solana is a thermal solar plant with the most energy storage in the US after pumped hydro — 1,680 MWh daily.

Arizona, along with Nevada, has been at the forefront of the battles over net-metering between utilities and rooftop solar, that hinges on too much solar by day, increasing the duck curve after dark.

Just this week the Arizona Corporation Commission (ACC) approved a drastic drop in net metering rates to shadow average utility-scale solar rates. Since utility-scale solar wholesale prices are much lower than rooftop prices, due to efficiencies of scale, that is a huge blow to rooftop in the state.

The decision “balances the economic benefits of grid-scale solar — which provides clean power to all of our customers at far less cost — with the desire of some customers to install solar on their rooftops,” said Arizona Public Service (APS) in a written statement.

Peak Loads are After Dark Now

Arizona is far from the only state trying to work out an arrangement that is fair to both utilities and those who invest in their own rooftop solar. …….

Finally, Utilities Would Value Dispatchable solar

Currently, utilities are incentivized to procure the cheapest solar. But a CPS would also offer utilities a better way to value dispatchable solar that can generate solar power after the sun goes down.

A thermal solar project like Crescent Dunes in Nevada can generate solar at any time of day or night, from stored solar energy in tanks of molten salts.

This Clean Solar Peak policy valuing stored clean energy is one foreseen by Nancy LaPlaca, who was Policy Advisor to former Commissioner Paul Newman at the ACC when it approved the solar storage contract between APS and Solana in 2013.

“We are underestimating the value of storage, as well as grid security,” she said to me at the time. “If the grid goes down in Phoenix on a very hot day, we will see the value of local storage that doesn’t depend on a long transmission line.”https://cleantechnica.com/2016/12/30/new-arizona-policy-mandate-solar-dark/