Use of renewable power generation is increasing worldwide, but as volume increases an obvious problem becomes more acute. Renewable energy sources, such as wind and solar, are intermittent. Despite claims by some suppliers to provide “100% renewable electricity,” in fact, without on-site energy storage to offset the times when sun doesn’t shine and wind doesn’t blow, this is not possible with current grid technologies. Base load plants, fossil fuel or nuclear, take up the slack when green power is not available. A second, more surprising problem occurs in areas, such as Germany, where there is high wind and solar capacity. California and Texas are forecast to have the same issue as wind generation grows. Without massive storage capacity, on a windy, sunny day part of the generation capacity is shut down because of lack of demand. Providers such as Green Mountain make it clear that their power simply flows into a tub that is mostly filled with fossil fuel energy. Power actually dispatched to customers comes mostly from fossil fuel sources. Higher “green” electrical rates simply pay for adding more renewables to the grid. Power from renewable sources is not actually fed to the buyer.
In order to accommodate more renewables, the grid system must be able to store excess energy for release during down times and peak load events. Managing a grid powered with base load nuclear and fossil fuel plants is relatively simpler because the supply is easily forecast and managed. Only the demand varies and demand forecasting is becoming more robust using high tech tools, such as GE’s Digital Energy products. Forecasting output of renewables is a big data problem, which IBM is tackling with HyRef software. China has decided to tackle the storage and forecasting problems with its Zhangbei demonstration project. Zhangbei is attempting to produce 670 MW of solar and wind power backed up with battery storage which can be reliably dispatched to their power grid. The battery solution, at this stage, is not cost competitive and is not being deployed in US markets.
The current limiting factor for renewables is akin to what the Oil & Gas industry refers to as “midstream” – the pipelines and other infrastructure that carries crude and gas from the well-head to the refineries and distribution points. Regions with highly reliable wind and solar are often far from power consumers. Transmission lines are expensive and cost-effective storage of energy produced when demand is less than output has not yet been developed. Currently, pumping water back above a hyrdro-generating facility represents 99% of installed storage capacity, with compressed air and flywheels about 0.5% and all battery storage less than 0.5%. Although battery technology is improving, there are physical limitations to the amount of energy that can actually be stored in a battery. China’s PV storage area is large, expensive, and a small drop in a huge bucket.
A Canadian producer of Hydrogen (H2) fuel cells, Hydrogenics, has proposed another solution which utilizes existing gas storage facilities and distribution pipelines as a component of the midstream solution. During the 2013 Total Energy USA Conference in Energy Storage the Game Changer for Europe and Beyond, Daryl Wilson, President of Hydrogenics, described in detail how the pilot for such a system is being deployed in Falkenhagen, Germany and other EU demo systems to increase renewables utilization rates. Production of H2 via water electrolysis during periods of excess capacity offers a scalable option. The Hydrogen can then be used as transportation or industrial fuel. It can be stored in existing natural gas storage tanks or pumped directly into the natural gas grid where it can be used for heating or as feed to power plants. Long-term, seasonal storage is also practical. Adding 32 MW of power to gas capacity at a 100 MW wind farm doubles the effective production while adding only 15-20% to capital costs. More importantly, this power is available for dispatch during peak loads.
In addition to mass energy storage, H2 fuel cells have a technical advantage over both batteries and generators as a source of portable power and as reliable, long-term back up power for critical infrastructure, such as large data centers. As increasing severe weather events continue to cause massive power disruptions with down-times measured in weeks, the demand is growing for secure, reliable, scalable back-up generation. Fuel cells are already technologically available to replace on-site back-up generators. If the cells are integrated into the building’s power management system and used for such purposes as reducing grid demand during peak events, they might already be cost-effective. In addition, portable fuel cells could also be deployed during large scale power outages.
To actually produce Zero Net Energy Buildings that can function off-grid, reliable long-term on-site power storage will be critical. A local DC power microgrid can use on-site solar, bio-fuel and/or wind to directly power lighting, electronics and even HVAC. Although some battery storage may be used, using excess power to produce H2 which powers fuel cells when renewables are unavailable is a more practical solution. In computer rooms, the fuel cells are now available for rack installation. In LEED buildings with on-site generation, fuel cells already make more sense than installing generators for power backup, as they can also be used to capture excess production.