Microgrids and the Distributed Energy Future

The promise of smart grid is creating a sustainable, scalable, modular, standardized approach to the power grid of the future.  Achieving this yoga-like perfection requires that we must simultaneously ‘go big’ and ‘go small’.

Going big means finding ways to bridge the gaps between the regional interconnects so new sources of clean energy can scale sufficient to be profitable.  This means building high voltage transmission to bring renewable solar and wind energy from remote locations to load centers to meet the state renewable portfolio standards.  Scale is also needed to make demand response profitable by giving constant energy management suppliers the ability to aggregate enough commercial and industrial customers to reliably supply the demand response product when called upon.

Going small means marshaling the inside the fence cogeneration and combined heat and power from industrial customers and build the microgrid networks of small scale commercial and residential players to enable net zero buildings.

What’s missing?

Energy storage is the key missing ingredient to the grand plan to create a reliable, sustainable distributed energy system enable both time-shifting and back-up in ways that reduce our dependence upon traditional fossil resources.  Reliable, cost competitive energy storage is a game changer that combined with microgrids to get customers to focus optimizing their own energy use by balance energy efficiency, demand response and self generation.

This isn’t some nuts and berries fantasy.  One of the largest microgrids in use today is at the University of California at San Diego that has turned its campus into an electrical lab using its microgrid to improve campus energy management and learning from that use to improve the science and technology of distributed energy. Now SMUD, the Sacramento Municipal Utility District is undertaking a similar but smaller scale project turning its own office complex into a microgrid for the same R&D purposes.

Building all this new technology requires standards to assure that the components work together and play together nicely when interconnected with the power grids across North America.  The microgrid SMUD is building will use the standards developed by CERTS. The CERTS system was among the first to standardize microgrid-grid interconnections.

The Consortium for Electric Reliability Technology Solutions (CERTS) was formed in 1999 to research, develop, and disseminate new methods, tools, and technologies to protect and enhance the reliability of the U.S. electric power system and efficiency of competitive electricity markets.  CERTS is a Department of Energy/California Energy Commission-led group focused on inverter technologies to allow the fast, safe disconnection and reconnection of microgrids to the larger grid essential to allowing microgrid power to serve as backup and stabilizer for the grid.

SMUD’s $3-million microgrid will include three 100-KW CHP combined-heat-and-power natural gas-fired generators, 10-KW of solar-photovoltaic panels, and a 500-KW battery for storage all located at the central utility plant at SMUD Sacramento headquarters.  One advantage of microgrids is that they can be assembled and put into service quickly from standard components.  SMUD’s project will go into service later this year.  The lessons learned will help SMUD promote and incorporate other microgrids on its system.  Longer term, the microgrid project is designed to cover the HVAC needs at SMUD’s headquarters and power its customer call center.

There are many players involved in this microgrid project with SMUD including CERTS which helped design the facility.  That design plan was tested with help by the US DOE and the California energy Commission at a test facility operated by American Electric Power.  Tecogen is providing the CHP reciprocating engine generators which recover waste heat for reuse by SMUD’s heating and cooling systems.  This integrated design improves the efficiency of the project from a typical 30% efficiency for the generators to 80% thus making the output much more valuable.

CERTS design for the project also uses digital power static transfer switches to monitor the power grid and seamlessly disconnect and reconnect without a reduction in power quality as required by most of the RTO/ISO grid operators in the event of a major system problem thus creating an “islanding” capability so they are able to operate in isolation from the grid.  Perfecting these techniques is a key part of assuring long term grid reliability in a smart grid enabled distributed energy future.