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| Fig. 1: Penzhinsk bay area map. (Courtesy of Google Earth.) |
A significant amount of planet's energy resources are located in places with relatively low population and lack of industries that may utilize such resources. Traditional way of converting energy to electricity and transferring it over AD/DC power lines may not work in case of long distances and high amounts of energy to be transferred, since typical power line has power carrying capacity of up to 1 GW. A good such example would be tidal power resources located as remote corners of the planet. Currently these resources are heavily underutilized due to higher cost compared to fossil-fuel based resources, however recent study shows that prices break even if one accounts for price of CO2 emissions for Kyoto-protocol countries. [1]
Penzhinsk Bay (Fig. 1) located at northeastern corner of Russia is known to have high tides with average tidal range of 6.8 ( close to 6.4 for Annapolis, Bay of Fundy) , which makes it a perfect place for construction of tidal power plants. [2] A few projects were proposed recently with average power generating capacity reaching 87 GW. [3] A few pilot projects were built to date, such as Annapolis Tidal Station [4] however significantly smaller bay size and single open centre turbine designed for minimum interference with marine life limits its performance to 20 MW.
Direct transport of electricity isn't feasible via conventional AC power lines because closest possible user that can utilize full capacity, Japan, is over 2000 miles away. Construction of multiple AC power lines is affected by significant power losses, climate of the region and lack of necessary infrastructure. As well as periodic nature of tidal electricity generation that will require building storage systems such as hydropump storage.
Attractive alternative is production of hydrogen via electrolysis and transfer of hydrogen over conventional underground pipelines that are more resistant to harsh environmental conditions.
Companies such as Statoil [5] or Norsk Hydro Electrolyzer [6] offer bipolar electrolyzers that can produce up to 500 m3 of hydrogen per hour at standard temperature and pressure, requiring 4.1-4.3 kWh/m3 of electricity. [4] An annual plant load factor of 0.45 as well as 10% of power required for maintenance and sea water desalination will result in an approximate average output of 107 m3/h, requiring around 2 × 104 large hydrogen generating plants to utilize full power generating capacity of the bay. Pipeline transfer of 107 M3/h seems to be technically feasible.
Use of tidal power may offer significant benefits both in terms of reducing CO2 emissions and getting access to cheaper (after CO2 emission costs are taken into account) electricity, however there are significant obstacles that currently prevent these power plants from being built - high capital cost that makes it highly dependent on available financing and interest rates, poor scalability - tidal barrier will have to be built across the bay which makes in uneconomical to operate at lower power outputs, location in remote areas that require transfer of energy in one form or another over long distances, as well as (in case of Penzhinsk bay) need to transfer significant amount of power over country border raises whole set of national security questions. Periodic mode of operation of such a power plant would require massive and expensive hydropump storage with capacity reaching tens of Gigawatts. An alternative solution is to produce hydrogen on site by electrolysis and transfer it via underground pipeline system which seems to be technically feasible. More detailed analysis including geopolitical factors is required to assess economic feasibility.
© Dmitry Pushkarev. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] " The Cost of Generating Electricity," U.K. Royal Academy of Engineering.
[2] M. F. Merriam, "Wind, Waves and Tides," Ann. Rev. Energy 3, 29 (1978).
[3] N. Barker and M. Westhead, "Managing Tidal Change," Winston Churchill Memorial Trust, Report WCMT/3-NB, May 2007.
[4] "Annapolis Tidal Station," Nova Scotia Power.
[5] "Hydrogen Technologies," Statoil.
[6] "Hydro Electrolyers", Norsk Hydro Electrolyers AS, October 2002.