Sunday, November 17, 2019

Power Down Resilience Part 2

                                                                                            written 10 November 2019
                                                                                        published 17 November 2019
            Last week I described the impact of the recent power down in Ukiah.  Two successive Red Flag weather events caused PG&E to shut down power for four days, costing over $9M in lost business and spoiled food.  Last year there were 19 Red Flag events, which could have cost over $70M.  From now on, we can expect the grid to power down several times every fire season, the result of 20th century grid design and decades of deferred maintenance colliding with a changing climate.  If we do nothing, our local economy is at risk, along with the state tourist industry and even the California real estate market.
            The citywide system I outlined last time, was just one way we could respond to this crisis.  I have since discovered that I underestimated the amount of land needed for the large array and the installed cost of a large battery.  The 100MW array would be about $200M and the 250MWh battery about $100M. This large expense should be considered as an upper end solution.  It would power the city as usual with no further changes to the rest of the infrastructure.  But in an emergency, we can survive with much less power, requiring less money, but invested in different ways.
            For example, we could install a battery pack in all 6,500 homes in Ukiah. A 13KWh Tesla Powerwall battery would run Internet and phone communications, a refrigerator, and some lights for 4 days or so.  A transfer switch would be required to select key circuits for backup power.  Such distributed storage systems are already being considered by communities in the Bay Area, with a focus on the low income and medical needs populations.
            A Powerwall and transfer switch wiring would cost about $15K per household, for a city wide cost of about $100M.  This distributed storage of 85MWh will cost about the same as one large 250MWh battery, reflecting the economy of scale with the larger installation.  Funding storage is the hardest part of any power resilience plan, since it has no direct economic return, but eliminates the greater costs of a power down.
            Timely installation before the next fire season would require more than a bulk order with Tesla.  The rewiring of each house requires a large skilled work force.  Local solar installers are already busy, so a job training program with this specific focus will be needed.  City inspection staff would have to be increased and the permit process streamlined.
            Once every home has installed storage, a range of options are available to extend emergency power resilience indefinitely by adding some power collection or generation.  A solar array as small as 1KW would suffice, costing about $3K per house, for a city wide total of about $20M.  Homes without good solar exposure could work together, installing a larger array where possible, powering everyone's batteries.  Alternately, a small generator running efficiently a few hours a day could keep the battery topped up.  Maybe the City would have a service bringing large generator trucks around to keep batteries full.
            An essential first step in any power resilience investment is increasing energy efficiency, reducing the power we need.  Two simple upgrades would change all lights to LED's and replace older refrigerators with modern high efficiency models.  The City has had efficiency rebate programs in the past, which could be funded at a higher level to upgrade the entire community in one year.  The electricity saved rapidly repays the cost of the new equipment.  By upgrading lights and refrigeration and installing distributed storage, we can make the residential portion of Ukiah more power resilient in the face of our new normal.  When everyone can stay in their own homes, with fresh food, lights, medical needs powered and emergency communications intact, we are all better off.
            If you like the idea of creating a "power down resilient" Ukiah, sooner rather than later, share these ideas with friends, and email your support to the City Council members below.
            There is no single way to accomplish this, and we need to pull together ideas from every part of the community.  If we show there is popular support for the basic vision, the Council will make it happen.