Robert McGillivray/ Director, Renewable Energy/ Hydrogenics Corp./ Mississauga, Ontario, Canada/ hydrogenics.com
Editors note:
One problem with wind power is that when the wind blows strong, the power it generates is either used or lost. In Europe, the utility rules are such that on windy nights when demand is low, wind generated power is almost given away.
A recent article in Windpower Engineering ( Solving the use it or lose it wind-energy problem, Feb 2010) reported on several devices and ideas for storing wind generated power. Hydrogen storage ideas, however, were not among them. To address the omission, Robert McGillivary offers ideas from his company.
Electrolysis is a controllable load that can be useful to RE power.
Renewable energy sources of power, such as wind and solar, are rapidly being adopted worldwide. They are an attractive source of electrical power because they are sustainable, have little or no emissions, and provide a domestic energy source rather than relying on costly energy imports. The costs of these technologies have continued to drop and governments are promoting their adoption with pricing and tax incentives. Wind farms and solar parks are now visible fixtures on the landscape across Europe, the U.S., and many other countries around the world.
However, there are a few problems with renewable energy, the main one being that it cannot be controlled the same way as traditional power sources. This is having a fundamental impact on the way grids operate. With a coal or natural gas power plant, the utilities and grid operators can more easily ensure that the load and power on a grid stays in balance. The way the grid has traditionally managed power this way: As the load fluctuates up and down, signals are sent to power generators to move up and down. But by deriving more power from uncontrollable renewable energy sources, we are upsetting the ability to control and balance the grid. What is needed is a way to manage this intermittent renewable power.
The HyStat electrolyser is in outdoor configuration.
One solution to this is to create more controllable loads that can be managed against the renewable sources. This need for controllable loads is the connection point to hydrogen fueling. A fueling station equipped with an electrolysis system uses electricity to generate hydrogen fuel from water, which is both zero emission and can be rapidly controlled over a broad load range. When grid operators are given control of this production, they effectively have a highly controllable load on their grid.
The plots for IMET electrolysis show on-off cycling (15 min on and 15 min off) and near vertical ramp rates.
In this way, the fueling station provides a service to the grid operator and utilities that either results in a revenue stream, or lowers the cost of power to the fueling station, or both. The end result is a more affordable source of hydrogen fuel for vehicle fleets. In addition, this delivery concept is not limited to fueling applications, which are still emerging. It can also be used with industrial hydrogen applications traditionally served by merchant gas sources of hydrogen.
Modern electrolysis products are based on mature and proven technology that is reliable and capable of continuous 24/7 operation in the challenging industrial environments. The Hydrogenics HySTAT system, for example, is an efficient, easy to install, modular package that can provide high purity hydrogen onsite and on demand.
Renewable energy incentives
Many grid issues are a direct consequence of the incentives provided to renewable energy power plants. One of the difficulties with financing wind farms and solar parks is dealing with the intermittent power profile relative to the way grid prices power production from conventional sources. Without guarantees to the power prices, it is more difficult to attract the investments required to build these facilities.
Government incentives such as feed-in tariffs have been extremely successful addressing the energy pricing uncertainty for renewable energy projects. Potential renewable energy developers are provided a guaranteed electrical rate independent of when they produce the power. Effectively, the grid operator is mandated to pay a set rate for renewable sources of power. However, this passes on the problem of renewable power intermittency to grid operators, who are left to deal with balancing the fluctuating renewable energy power with loads. For small amounts of renewable energy, this can be done with existing assets and conventional control strategies. But as renewable energy becomes a bigger part of a particular grid, the intermittency on the power supply side becomes more unmanageable.
The layout for a vehicle fueling station would include individual dispensers that are not shown.
The shortest term control mechanism for grid stability at the disposal of grid operators is ancillary services, which are traditionally supplied only by power generators. As the amount of renewable energy sources on the grid increases, the value of ancillary services will certainly rise. This has been the experience in Germany, Denmark, and California where similar renewable energy incentives are in place.
Controllable loads
Loads can provide frequency regulation and operating reserves that meet or exceed power generators and loads will typically have high response rates and short cycle times. In areas such as California and Texas, loads often provide at least 50% of the ancillary services needed. Pricing markets have been introduced to economically drive the providers of these services.
Controllable loads are an important tool for grid operators to control the grid, balance supply with demand, and alleviate local transmission constraints. Electrolysis can be used to provide utility scale load control for grid balancing. In fact, the connections back to hydrogen are already being made. In 2009, Germany announced projects to implement hydrogen energy storage1 and hydrogen vehicle fueling2 as a means to dispatch this power.
Electrolysis
Electrolysis systems can ramp up and down quickly without adverse effects. One such system, Hydrogenics HySTAT electrolyzer, operates over a wide range of capacities from 10% to 100% of rated load for large, multi-stack systems. If the system has storage, as is the case with fueling stations, electrolysis can operate at different times from the fueling of vehicles, for example. These vehicles could be cars but more likely they would be city busses powered by fuel cells. In the industrial market, hydrogen is used for its mechanical and chemical properties in applications such as float glass, semiconductor manufacturing, optics production, metal annealing and sintering, high temperature flames and hydrogenated oils.
The company’s HySTAT electrolysis product line is modular with building blocks of 365 kW (60 m3/h hydrogen output). Multiple systems are often delivered to a single site achieving 1 to 5 MW and very large-scale system concepts could achieve 10 to 100 MW. The hydrogen generator is containerized and available with a compression, storage, and dispensing package to match the needs of the vehicle fleet.
Hydrogen can be used as a transportation fuel with over 150 fueling stations around the world supporting demonstration programs for buses, cars, and vehicles such as forklifts. A fleet of 100 municipal buses would consume about 3.8 tones of H2/day given typical bus routes. If supplied with electrolysis, this would represent about 10 MW of continuous load.
The Proterra bus (left) is powered with a 32-kW fuel cell, the ZEV bus (middle) is powered by a 16-kW fuel cell, and the Tecnobus uses a 12-kW fuel cell.
This is not a new concept. The company has provided electrolysis equipment for over 35 fueling stations worldwide including one program European called CUTE and stations in California supporting bus and car fleets. Fueling stations and the load could be in several locations allowing load control to address transmission constraints as well as load balance and ancillary services. With the appropriate amount of hydrogen storage, there would be no impact on the station’s bus users potentially for many hours or even days.
Benefits of renewable hydrogen fueling
Use an electrolysis load for ancillary services gives a grid operator an additional tool to manage grid intermittency. A controllable load offers significant advantages over controllable power sources for ancillary services and demand response, such as a:
Zero-emission fuel. Hydrogen from electrolysis produces no incremental emissions and provides a totally clean and green connection between renewable energy sources and zero-emission transportation using hydrogen fuel.
Additional income stream. By delivering ancillary services, the electrolysis system generates an additional income stream, effectively lowering the cost of delivered hydrogen for either industrial or transportation applications.
Frees power resources. Load for ancillary services frees the power generation systems to focus on only providing power.
Better response rates. Loads also provide a better response to control-center requests. Loads can typically respond more quickly as opposed to large systems that have slower response rates.
Alleviate transmission problems. The modular nature of electrolysis loads also allows broadly distributing it across a particular grid. This provides the additional opportunity to balance load, provide ancillary services as well as address transmission constraints. For instance, if an area with five large electrolysis fueling stations has a transmission problem in a location with one of the fueling stations, that station could be temporarily turned off until the problem was resolved.
Modularity and redundancy. Modularity makes the overall system less prone to large-scale failure, decreasing a need for redundancy in overall contracted ancillary services.
Efforts to promote the adoption of renewable energy sources on grids and hydrogen vehicles for transportation need not be independent. They can be linked with hydrogen electrolysis in a way that is highly complementary. Hydrogen vehicles and fueling can provide the important controllable load that renewable power sources need for high penetration into a modern grid. Modern electrolysis has the opportunity to simultaneously change the way we generate, store, and use energy on grids and in transportation.
1 “Merkel launches building of revolutionary hybrid power plant”, Press release April 29, 2009
2 “Firms to build up German hydrogen infrastructure”, Press release Sep 10, 2009
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