Flexible Technology with Large Applicative Potential

Demonstration units such as the Schatz Solar Hydrogen Project stand­alone energy system, which has powered since 1991 the 600 W air compressor that aerates the aquaria at Humboldt State University’s Telonicher Marine Laboratory in Trinidad, California, clearly show that

 

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Figure 2.25 The low cost hydrogen compressor developed by RE Hydrogen in the UK.

(Reproduced from Rehydrogen. com, with kind permission.)

hydrogen can be used efficiently to store solar energy and that the electrolyzer is flexible enough to respond to the fluctuating solar energy yield with respect to both time and capacity.48

The system – the first solar hydrogen energy plant in the USA – consists of a 7.5 kW PV array, a 6 kW alkaline electrolyzer, a 1 kW 120 V AC inverter, and a 1 kW PEM hydrogen fuel cell. During the day, the system uses energy from the sun to power the compressor directly and to produce hydrogen that powers the compressor at night, when the sun is not available (Figure 2.26).

The electrolyzer incorporated into the system was a medium pressure alkaline electrolyzer able to deliver 20 standard liters per minute of hydrogen gas at a current of 240 A at 240 V. The hydrogen gas produced (at a pressure of 7.9 bar) was stored in three conventional tanks with a total capacity of 5.7 m3 and provided approximately 133 kWh, which operated the load (600 W) for 110 hours, assuming a fuel cell efficiency of 50%. Over eight years of operation each system component had the following efficiencies:8 •

Chapter 2

 

During the day…

 

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Oxygen

 

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water

 

Oxygen

 

Water

 

Fuel Cell

 

Elecuolyzer

 

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Air

Compressor

 

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Figure 2.26 Since 1991, a compressor at the Telonicher Marine Laboratory in Tri­nidad, California has used energy electrolytic solar hydrogen to power the compressor when the sun is not available.

(Reproduced from Ref. 48, with kind permission.)

 

• Voltage 84.0%

• Fuel cell 43.1%

• Overall electrical storage 34.0%

Further, and much larger, demonstration units such as the German – Saudi HYsolar installation, an experimental solar-powered water elec­trolysis plant operated near Riyadh in the 1990s in a cooperative relationship between Saudi Arabia and Germany, confirmed that the electrolyzer coupled to a PV array is a suitable technology to produce large amounts of clean hydrogen from water and sunlight only.49

In the 1990s, however, the retail price of PV modules exceeded 8-10 $W-1 and each module was losing >1% of the originally rated power. Indeed, after 15 years of operation, in 2006 the Schatz Lab solar hydrogen project was still running, but the PV array that once produced 7.5kWp was degraded by 16%.50

Today modules with linear loss in output power are easily available (Figure 2.27), and the cost of PV electricity has dropped to less than 0.7 $W-1.51 This means that solar electricity has already achieved grid parity with conventional electricity in many regions of the world, including southern Italy, Greece and Spain. It is perhaps not surprising,

 

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Figure 2.27 According to this manufacturer’s guarantee, the actual power of a new module cannot deviate from the specified rated power by more than 3% during the first year; and afterward, the power will not decrease by more than 0.7% of the rated power per year. So, at year 20, the module’s capacity is guaranteed still to be at least 83% of the nameplate. (Reproduced from Solarworld. de, with kind permission.)

 

Low cost H2 and 0, generation on small scale from renewable energy

 

Ekctrolyser

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renewable energy

Figure 2.28 Low cost generation of hydrogen and oxygen from wind and solar electricity opens the route to multibillion world markets.

(Adapted from a figure by Dr A. Roy, with kind permission.)

 

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then, that numerous new commercial solutions to generate hydrogen from PV electricity are eventually reaching the market.

In other words, with low cost electrolyzers and compressors and given the now low cost of PV electricity, described in detail above, small-scale hydrogen production (Figure 2.28) becomes a convenient way to capture and store energy from renewable sources and provide fuel for hydrogen- powered vehicles in place of large-scale infrastructure, as well as for

Подпись: Novel compressors can be used in all of the markets related to electrolyzers and fuel cells. There are > 5000 petrol stations and 5500 electrical substations in every major EU country, each of which could potentially install hydrogen compressors for energy storage applications. The fast expanding fuel cell market will need a green hydrogen supply and compressed gas storage.Подпись: A significant amount of surplus electricity exists on the grid at times, due to the mismatch between demand and supply and due to the grid constraints. The surplus of wind and PV that cannot be dispatched from solar and wind farms due to the grid’s inability to absorb power at a given time can be made available to electrolyzers for storage, and later on used to supply 24/7 electricity.Table 2.7 Market segments for efficient water electrolyzers and hydrogen compression technology. (Adapted from Ref. 1, with permission.)

Market segment 1: onsite Market segment 2: Gas

hydrogen and oxygen compression and vehicle Market segment 3: smart

production refueling grid and energy storage

Currently the majority of the hydrogen market is served by gas supply companies. New electrolyzers can be used to produce hydrogen and refill hydrogen cylinders, and create an end-to-end supply chain network for hydrogen production, distribution and utilization. In the UK alone the estimated size of this market segment is £500 million per year. A relatively large and separate market also exists for oxygen.

industrial usage, opening the route to multibillion world markets. New, efficient water electrolyzers and hydrogen compression technology are suitable for several market segments, from energy storage, grid balan­cing, solar fuel-based power generation, and transport applications (Table 2.7).

There is little doubt that hydrogen produced by solar and wind farms will help to balance the wholesale electricity price, providing also a crucial service for grid stability.

For example, in Canada, a manufacturer of hydrogen generation and fuel cell products, Hydrogenics, recently completed a successful trial with an Ontario electricity utility, demonstrating the viability of elec­trolyzer technology for utility-scale grid stabilization (Figure 2.29).52 During the trial period, the load from the company’s electrolyzer provided frequency regulation in Ontario by responding to power reg­ulation signals from the utility on a second-by-second basis, thus demonstrating how hydrogen electricity ensures better balancing of electrical supply and demand while alleviating local transmission con­straints. The company announced that it will apply lessons learned from the Ontario project in the development of megawatt-scale energy storage applications.

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Figure 2.29 The HySTAT electrolyzer from Hydrogenics was used in Ontario to demonstrate that hydrogen energy is an excellent new way to balance supply and demand to and from the grid.

Another interesting commercial product that uses electrolytic solar hydrogen as fuel is the Riviera 600 electric boat.53 With a range of 80 km with a full hydrogen tank, the boat is 6 m long, 2.2 m wide and weighs 1400 kg. The 47% efficiency of the noise-free 4kW fuel cell engine should be compared to the 18-20% efficiency of a conventional internal combustion engine.

Refueling with compressed hydrogen is relatively fast and simple (Figure 2.30). The boat’s fuel system consists of a 20 kg cartridge that can be charged with up to 0.7 kg of hydrogen kept at 350 bar. Refueling is done using a standard filler, plus simple exchange of an empty car­tridge for a full one. Compared with battery-powered electric boats, the hydrogen-powered electric boat requires only five minutes to refuel, whereas for conventional electric boats 6-8 hours are typically required to recharge the spent batteries. Moreover, the Riviera 600 electric motor has twice the range of conventional battery-powered boats.

To generate electricity, a hydrogen refueling station makes use of PV modules integrated in a 250 m2 flat roof (Figure 2.31), further connected to an electrolytic cell. Even at Austria’s cold latitudes this station is capable of producing an annual yield of 823 kg hydrogen, equivalent to 1100 cartridges with a 27 200 kWh energy content, enough hydrogen to run a boat for 80 000 km. The ‘‘Future Project Hydrogen’’ team has created budget calculations for the generation of hydrogen on-site by use of PV cells on the premises of 10 boats for commercial use (for example within a boat rental company).

Подпись: Figure 2.30 Refueling of the Riviera 600 Frauscher boat is done in five minutes using a standard 350 bar filler coupling plus simple exchange of an empty cartridge for a full one. (Reproduced from Frauscherboats.com, with permission.)
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Chapter 2

For comparison, storing power in batteries over long periods of time is linked to huge losses due to self-discharge (5-10% per month), while the energy density is a fraction of that for hydrogen, which means that storing energy in the summer in a battery of the same capacity would mean that no energy was available in winter.

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Figure 2.32 Made of passivated steel and 1 km in length, the first underground hydrogen pipeline in the world has been built in the Italian city of Arezzo and delivers pure H2 at 3.5 bar to the fuel cells installed in four goldsmith companies.

(Reproduced from Ref. 54, with kind permission.)

Another example which shows that PV renewable hydrogen is far from being solely a research topic, is afforded by the world’s first underground pipeline, which supplies H2 to five customers in the Italian city of Arezzo, with a main channel of around 600 m (Figure 2.32).54

Solar hydrogen is generated by water electrolysis via PV modules over the roof of an off-grid building (HydroLAb, Figure 2.33), using four 5 kW hydrogen fuel cells and two 1 kW fuel cells to produce both elec­tricity and heat for the whole building.55

Today, when solar panels generate more electricity than a home can use, the excess is simply fed back into the grid, essentially subtracting from the homeowner’s utility bill. In an off-grid application, the excess is put into batteries, but fuel cells are more versatile and their price is declining rapidly.

Finally, an interesting approach to electrolytically generate hydrogen without the requirement for hydrogen storage has been introduced recently by Honda in the USA, with its Solar Hydrogen Station (Figure 2.34).56 Users slowly refill their fuel cell vehicle overnight (an eight hour fill produces enough hydrogen, 0.5 kg, for a typical day’s driving), by using

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Chapter 2

less expensive off-peak electrical power purchased by the grid at $0.05 kWh-1 or even less. During daytime peak power periods, the Solar Hydrogen Station exports high-valuepeak solar electricity to the grid, providing a cost benefit to the customer.

Designed as a single, integrated unit to fit in the user’s garage, the new Honda hydrogen station reduces the size of the system, while the intui­tive system layout enables the user easily to lift and remove the fuel hose, with no hose coiling when the hose is returned to the dispenser unit.

The previous solar hydrogen station system, studied by Honda in California since 2001, required both an electrolyzer and a separate compressor unit to create high pressure hydrogen. The compressor was the largest and most expensive component and reduced system effi­ciency. By creating a new high differential pressure electrolyzer, Honda engineers were able to eliminate the compressor entirely. This innova­tion also reduces the size of other key components to make the new station the world’s most compact system, while improving system effi­ciency by more than 25% compared with the solar hydrogen station system it replaces.

One of the main messages of this book is that it has been the pro­longed lack of hydrogen filling stations, both on large and small scales, that has caused the failure of hydrogen energy development in the last 20 years. Companies and local governments seem now to have understood this major gap and have started to deploy hydrogen refueling stations that use electrolyzes and renewable energy, namely PV or eolic elec­tricity depending on the site location.

Figure 2.35, for example, shows the recent case of Hempstead, a town in New York state, where a 100 kW wind turbine provides the energy

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Figure 2.35 The town of Hempstead, New York, located its Conservation and Waterways Department in Point Lookout; a 100 kW Northern Power 100 wind turbine was completed at Hempstead’s hydrogen station. (Reproduced from greenfleetmagazine. com, with kind permission.)

necessary to create the hydrogen gas needed to power the town’s fuel cell

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cars. 7

Powered by winds off the Atlantic coast, the wind turbine is capable of generating up to 180 MWh of energy per year, providing an almost continuous source of low cost energy to split water. The resulting hydrogen fuel is dispensed from Long Island’s only hydrogen fueling station, located adjacent to the turbine. The excess energy generated by the turbine will be fed into the town’s grid, resulting in annual energy cost savings for local customers of the electric utility estimated at approximately $40 000. Overall, the wind turbine and hydrogen energy will save money, conserve natural resources, create jobs and provide smooth and pollution-free mobility to the town’s citizens.

Updated: August 16, 2015 — 9:13 am