Page 146 - Zero Net Energy Case Study Buildings-Volume 3

PREFACE TO CASE STUDY NO. 17 STANFORD UNIVERSITY
(Overleaf, previous page)
Aerial view of the completed Central Energy Facility.
(Opposite page) Views of the Stanford Solar Generation Station in the Mojave Desert of California.
(Photos courtesy of Sun- Power.)
132
Plan for Renewable Energy Supply
The final piece of the plan was the connection to a solar PV energy system large enough to sup- ply electricity at a substantial part of the entire Stanford campus demand. Since land and existing building rooftops were limited at the campus, a large-scale solution away from the campus had to be devised.
The solution was found in the Direct Access Program2 passed by California legislature in 1998. (This program was suspended in 2001 and reinstated in 2010.) Stanford University was eligible to participate in the program beginning in 2012. Under this program, Stanford entered into a power purchase agreement (PPA) with a third party provider, the solar energy company, Sun- Power, to obtain electricity from a new 68 MW solar electric “plant”, called the Stanford Solar Generation Station, consisting of 155,000 PV panels located in the Mojave desert north of Palm- dale, California.
According to California law, the transmission wires from the desert to the Stanford campus are managed by the “non-profit public benefit corporation”, California Independent System Operator (Cal ISO). The parties to the PPA include the public electric utility (in this case, Pacific Gas & Electric Company), which provides the equivalent amount of electricity to the Stanford campus as put into the grid by the SunPower plant. The terms of the agreement are in effect for 25 years.
The solar power plant provides 53% of the current electric power demand of the entire Stanford University campus at 20% less cost than that expected if Stanford had purchased the directly from the electric utility for the new energy-efficient CEF. There has been a campus facilities program to install solar on new and existing campus buildings and those systems contribute an additional 5 MW, which is an additional 7% of the total electric demand. This brings the total renewable energy supply for the campus to 60% of total campus electric demand.
This is a significant advance down the path to a total ZNE campus, accomplished in less than 10 years from the start of concept planning.
The combined systems of the Central Energy Facility and the Solar Generating Station constitute the Stanford Energy System Innovations (SESI).
Post Construction Performance
In the first year of operation, the new CEF used only 5% of the natural gas total that was typical of the old cogen plant. This was due only to the operation of the OSHPD plant for the Stanford hospitals. Electrical energy use unsurprisingly increased, requiring 33% more draw from the grid, but the peak electrical demand was significantly lower because of the thermal storage—38 MW peak compared to the typical 45 MW peak of the old cogen plant.
2 For more information about the Direct Access Program, see https://www.pge.com/en_US/ business/services/alternatives-to-pge/electric-services/direct-access-electricity/direct-access- electricity.page
Zero Net Energy Case Study Buildings: Volume 3