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Volvox (Engineering) Ltd | |
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A sustainable alternative to the grid |
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MultiSpeed as a CHP with the grid used for night-time and 'low demand' supply
We know we need electricity every minute of every day, but we don't want to run our generators all that time. The usual solution is to charge a Battery Bank and use the power from that during periods of low demand. However, unless you are completely unable to use grid power (as with many of our customers), you might want to build a system like this. This customer's premises were costing him £000's per quarter in electricity bills, so he built a fantastic system that was relatively simple, but extremely reliable and effective. The grid is used for low load times instead of a Battery Bank, and the generator used when demand was high. An exhaust gas heat exchanger was added to capture all the generator's waste heat, and plumbed into the premise's central heating. This is a great strategy because your heating requirements usually peak at the same time your electricity demand peaks, and the cost of grid electricity drops when demand is low (i.e. at night time). A relay switch is used that can switch the source of electricity between generator and grid supplying the premises. The relay is activated by a 240VAC supply - when the relay (switch terminal) is given no 240VAC supply, it switches grid power to the premises. When the relay (switch terminal) is given 240VAC it switches the grid off and power is supplied from the generator. This is a wonderfully safe, effective and simple method of integrating a generator with the grid. The output from the generator is connected to the switch terminals on the relay, so that whenever the generator started, the grid would be disconnected (and generator connected). With this wiring in place, all that is needed to do is switch the generator on, and you get heat from the generator and no electricity charges from the grid. The remote switching facility of the MultiSpeed is then used to connect a timing switch (the same as the ones used to switch your central heating on and off) to turn the generator on and off when you know electricity demaind is high (on in the early morning and most of the evening, and off in the afternoon and nght). The timer switch starts the generator. The power from the generator activates the relay disconnecting the grid from the premises and connecting the generator to the premises. The transition is unnoticeable. [N.B. An alternative variation on this strategy would be to use a thermostat in your premises to switch the generator on and off, but in this case study, a timer was chosen as this is more cost-focused than comfort-focused]. |
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Here's the engine room. With the IBC fuel tank visible above. |
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Here's the control panel with the starter battery below. The pulley wheel visible at the bottom left is actually a spare - used for changing the speed (pumping rate) of the water pump. |
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The exhaust gas heat exchanger is visible here. The square black flange is where the exhaust pipe attaches, and the water pipes can be seen entering tangentially. It has all be insulated to minimise losses. |
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The exhaust system and heat exchanger can be seen here, together with the water pipes that provide heating for the premises. |
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A flexible coupling in the exhaust has been used to stop the engine vibration from travelling into the heating system. Again, it is all insulated to avoid heat loss. |
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The exhaust gas heat exchanger should be treated in the same way you would a boiler. So here you can see a standard central heating water pump, used to circulate the hot water. |
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The power cables can be seen here. |
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Here's the gadget (relay) that makes this whole setup work. There are plenty of ways to get the wiring wrong, but it's all very logical and the switching layout is drawn on the relay. Just makes sure you test it before you 'go live'. | |
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And if you want to buy one, the numbers and specification can be seen here. | |
