We interrupt this thread on the helicopter briefly to mention the latest saver of the Planet. The Searaser and some of its simpler engineering aspects.
This is another proposal for generating electricity in an environmentally friendly way. The media is again trumpeting it as encouraged by press releases. http://www.guardian.co.uk/environment/2012/jan/23/bicycle-pump-searaser-energy?INTCMP=SRCH
The fact that the media say that it works like a bicycle pump does not induce confidence. The inventor’s backers Ecotricity [http://www.ecotricity.co.uk/our-green-energy/our-green-electricity/and-the-sea/searaser] call it a double acting pump. It cannot be both. Virtually all bicycle pumps only push air into a tyre on the inward stroke; that is, it is single-acting. A double acting pump pushes its fluid both on the inward stroke and the outward stroke.
The Searaser is another oscillating device submerged in the friendly sea. The Unique Selling Point is that it generates its electricity on land to avoid electricity in the water. It is simple enough in principle. A large float at the sea surface bobs up and down with the waves. A rod attached to it passes down to a simple piston pump which is tethered to the sea floor by a cable. http://www.youtube.com/watch?v=_9jGis5V5LE
The Lad has to wonder how reliable such an arrangement can be as it flops around in the turbulence of the open sea. The pump and the float will each be subject frequently to different forces tending to flex the assembly. Even if the float and pump themselves can withstand these forces without failure; the piston rod seal at the pump will see large leverage forces. They will tend to make it leak or, at the least, make for inefficiency due to high friction. What is the L/D ratio for the bearing?
Speaking of friction, how much power at the pump is wasted through friction losses pushing the water through pipes from the pumps miles out at sea all the way to the land and its power generating turbines?
Each pump cannot be scaled up beyond the scale set by the sea wave length. If it is built much bigger than, say, one or two wavelengths like a ship, it will become stable – like a ship – and not move up and down at all or very little.
Full engineering design and development details cannot be expected to be given in the press. It seems clear to The Lad though that there is a very long way to go before the engineering production model is workable. Even then the economics will still be an unconquered enemy.
Note also that a reservoir is needed on land at a suitable height. This is to provide enough potential energy to generate a useful amount of power whilst not needing too much pressure head. Too high a working pressure for the system will lead to even more design problems. The storage of water in the reservoir is also needed to smooth out the variations in pressure inherent with an oscillating pump and also to provide some back up for these days, and they undoubtedly exist even in the UK, when the waves are small or in a flat calm.
But again, how big will the reservoirs need to be for every pump farm to provide continuous power and not have its beneficiaries sitting in the dark. After all the UK weather is known to everyone to vary from day to day. There tends to be a comparable number of weather states that are “too much” or “too little” as there are that are “Goldilocks”.
The video shows the first model giving some squirts of water that are, not to put too fine a point on it, not very big. Perhaps that is the origin of the Bicycle Pump name. Later models seem to give a better flow rate, it has to be admitted. Nonetheless, still the supporters of such proposed systems still cannot show, even if they understand it, the gigantic amounts of unremitting, 24/7 power generated by the Base Load Power Stations for a modern society.
The Lad is aware of an existing water power generating scheme on a nearby, quietly flowing river. To see the amount and velocity of the outflow which generates only 150kW is a reality check on the water flow and plant required. This is how it can, more realistically, be done. Visit here to see something of it; http://www.derwent-hydro.co.uk/our_sites/index.html . The Lad has no connection at all with this small organisation.
So, assuming that much can be done to develop the system, how many fully-engineered assemblies would be needed to generate, say, a megawatt hour of electricity? What is the cost per unit of electricity from such assemblies at the Grid?