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<a href="../201208/29 --Apple-Mail-172-724061569 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Hi Dave, On 29-Aug-12, at 10:48 AM, David & Alison Webster wrote: > Dear All, Aug 29, 2012 > An objection to wind power, that continues to surface, is the > failure of potential wind generation to reliably match demand for > electricity. > > Are there compelling reasons, given suitable topography or > infrastructure, why excess wind power could not be stored by pumping > water to a higher reservoir or by generating hydrogen ? Geoge Monbiot's book "Heat: How to stop the planet from burning" includes an extensive discussion of this topic. By far and away the most efficient way to store energy generated from wind is in reservoirs (i.e., pumping water uphill when there is excess wind supply and then letting it flow downhill through a turbine to generate electricity when demand is greater). Depending on details of how the reservoir and generation system are constructed losses involved in such "pumped storage" are only in the range of 20-25% (i.e., one is able to recover 75-80% of the energy that goes into the process). This is much better than any of the alternatives such as electrolysis of water or compressing air in underground caverns which typically involve losses of 60% or more. There are other more exotic possibilities such as flow batteries, flywheels, or superconducting magnets that can store limited amounts of energy and only for short periods of time. However, there is another way of skinning this cat. Electric transmission lines in most of the world use AC (alternating current) which has no inherent capacity to store energy. However, some jurisdictions are moving to high-voltage DC (direct current) lines (for a large variety of reasons too lengthy to go into here). The upshot is this: a large DC line (there is already one in Africa that runs 1,700 km) functions to some degree like a very large battery. One can (within limits) continue to pump electricity into it, progressively stepping up the voltage. Then when you need power you run it out of the line through a transformer. The more extensive a DC grid the greater the overall capacity of the "battery." Moreover, with the development of new high-voltage DC valves and much lighter wires the costs of DC transmission are dropping sharply and their environmental impact is less. Cheers! Chris Christopher Majka - columnist, Rabble.ca Halifax, Nova Scotia, Canada Email: c.majka@ns.sympatico.ca http://rabble.ca/blog/26142 "The significant problems of our time cannot be solved by the same level of thinking that created them." - Albert Einstein --Apple-Mail-172-724061569 Content-Type: text/html; charset=US-ASCII Content-Transfer-Encoding: quoted-printable <html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space; ">Hi Dave,<div><br><div><div>On = 29-Aug-12, at 10:48 AM, David & Alison Webster wrote:</div><br = class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div>Dear = All, = &n= bsp; Aug 29, = 2012<br> An objection to wind power, that continues to = surface, is the failure of potential wind generation to reliably match = demand for electricity.<br><br> Are there compelling = reasons, given suitable topography or infrastructure, why excess wind = power could not be stored by pumping water to a higher reservoir or by = generating hydrogen = ?<br></div></blockquote></div><br></div><div><br></div><div>Geoge = Monbiot's book "Heat: How to stop the planet from burning" includes an = extensive discussion of this topic. </div><div><br></div><div>By = far and away the most efficient way to store energy generated from wind = is in reservoirs (i.e., pumping water uphill when there is excess wind = supply and then letting it flow downhill through a turbine to generate = electricity when demand is greater). Depending on details of how the = reservoir and generation system are constructed losses involved in such = "pumped storage" are only in the range of 20-25% (i.e., one is able to = recover 75-80% of the energy that goes into the = process).</div><div><br></div><div>This is much better than any of the = alternatives such as electrolysis of water or compressing air in = underground caverns which typically involve losses of 60% or = more. </div><div><br></div><div>There are other more exotic = possibilities such as flow batteries, flywheels, or superconducting = magnets that can store limited amounts of energy and only for short = periods of time.</div><div><br></div><div>However, there is another way = of skinning this cat. Electric transmission lines in most of the world = use AC (alternating current) which has no inherent capacity to store = energy. However, some jurisdictions are moving to high-voltage DC = (direct current) lines (for a large variety of reasons too lengthy to go = into here). The upshot is this: a large DC line (there is already one in = Africa that runs 1,700 km) functions to some degree like a very large = battery. One can (within limits) continue to pump electricity into it, = progressively stepping up the voltage. Then when you need power you run = it out of the line through a transformer. The more extensive a DC grid = the greater the overall capacity of the "battery." Moreover, with the = development of new high-voltage DC valves and much lighter wires the = costs of DC transmission are dropping sharply and their environmental = impact is = less.</div><div><br></div><div>Cheers!</div><div><br></div><div>Chris</div= ><br><br><div apple-content-edited=3D"true"> <span = class=3D"Apple-style-span" style=3D"border-collapse: separate; color: = rgb(0, 0, 0); font-family: 'Times New Roman'; font-style: normal; = font-variant: normal; font-weight: normal; letter-spacing: normal; = line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: = 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: = 0px; -webkit-border-horizontal-spacing: 0px; = -webkit-border-vertical-spacing: 0px; = -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: = auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div = style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space; "><span class=3D"Apple-style-spa