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Volvox (Engineering) Ltd | |
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A sustainable alternative to the grid |
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!!!!!!!!! In progress!!!!!!!!!!!
Here we have the main office premises of Energy Solutions Ltd., in Wembley. The company is a renewable energy specialist consultancy that has vast experience in many related technologies. The office space is approximately 100 square feet and is heated by a combination of solar panels and a Volvox Multi-Speed CHP unit. They also have Photovoltaic panels which are used to supply power t the grid. The objective of this project (which is still in progress, as you see below) is to use the CHP for space heating, and sell the electricity generated by the unit, back to the grid. The fuel used is waste vegetable oil. |
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Here is the Energy Solutions premises. The building is a converted church, and is actually built correctly (vertically), though the photo has somehow given the appearance that the building is leaning - it isn't. The engine shed is shown here to the left of the picture. |
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Here's a closer picture of the engine shed. In true Energy Solutions style, it is constructed from compressed soil (well, local clay and aggregates). Being a relatively unknown building material, this has added increased concern about vibration. More on that later. The compressed soil walls are built on top of a substantial concrete base. |
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Here's a view of the CHP unit inside the engine shed. The project is still a long way from completion, but is now fully functional. The CHP unit is fitted with an Exhaust Gas Heat Exchanger, which is plumbed in series with the engine cooling system. A central heating pump pumps the water directly to a large water tank (the heat store) which is also supplied by heat from the solar panels. The CHP unit is currently setup to run at 850rpm allowing it to provide approximately 4.5 kW of electricity. We are hoping to get (though we have yet to measure it) approximately 8kW of heat from the unit at this speed and electrical load. |
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In an attempt to ensure any vibration does not do any damage to the compressed soil walls of the building, a spectacularly large lump of concrete has been used to mount the unit on. Unfortunately this hasn't quite solved the problem, so we are now fine-tuning the balance of the engine using a strobe light and small lead weights bolted to the flywheels. We also plan to add a rubber mat between the Genset and concrete block. This will certainly help reduce/eliminate the vibration into the walls, but will also allow the engine to move a little, allowing us to see the vibration under strobe lighting. |
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Here's the grid connection, reassurringly decoupled by an isolation switch with a pad lock on it. We haven't yet performed our first grid connection here, though we have done it at another site (see Case Study 5, when it's published) using the 'two light bulbs between the grid and Genset lives' method - it worked great! | |
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Here's our Exhaust Gas Heat Exchanger (curtesy of Steck Depositors Ltd). The exhaust gas enters at the top right and leaves the unit at the bottom left, having travelled through three sets of 9 tubes. As you can see, it is made of stainless steel, and the energy meter can be seen at the top. |
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Here's our oil level monitoring method. The oil drain plug is a 3/4" BSP female, allowing standard plumbing fittings to be used to bring the oil exit to a more accessible point. A transparent inspection tube shows the level of the oil, and the tap is used to drain the oil. |
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Here's the coolant (primary circuit) circulation pump. As you can see, it is currently mounted in a very temporary manner, waiting for a bracket to be made that will replace the lifting eye on the alternator. Cool water from the (large) coil in the heat store (water tank) is pumped into the Exhaust gas heat exchanger (EGHE). It then flows out of the EGHE and into the bottom of the cylinder block. It then comes ou of the top of the Cylinder head and flows on back to the heat store coil. |
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A header tank is required to allow for expansion/contraction of the water in the system. The air intake silencer is also shown in his picture - it's very good at reducing the intake valve clatter. |
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Here is a marginally better picture of he energy meter. It a solid state CPU board that takes readings fro a choice of two (of three possible) temperature sensors and one flow sensor. It hen calculates the difference between two temperature readings, multiplies this by the water flow rate, and displays a heat transfer value in kWatts. I can, of course, also show the actual temperatures experienced by each sensor, and show the flow rate. This device is again curtesy of Steck Depositors Ltd. |
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This picture shows (though not very well) the flow sensor (centre slightly left), one of the temperature sensors (in the water manifold from the cylinderhed - top right), and the fuel pre-heater on the high pressure pipe (top centre). The glow-plug can also be seen to the left of the water sensor. | |
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This picture shows the overheat cut-out switch (also known as the switch that you'll find on your hat water tank that regulates the immersion heater). We have always intended to replace this switch with something a little smaller and tidier that doesn't need straps to keep it in place. However, over time, this very simple, durable and reliable switch is gaining popularity. The switch is wired in series with the remote switching circuit, so that when the switching temperature is reached, the generator shuts down until the temperature drops. |
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This picture shows the only silencer in the system. It is an 'off the shelf' item from Servais Silencers Ltd. All their products are extremely good value for money. They also supplied the air intake silencer. The EGHE has been designed to take the temperature of the exhaust down to below the water condensation point, thus capturing the latent heat of condensation. This means that there is quite a lot of water (not steam) in the exhaust gas, and most of this is dumped in an expansion vessel just visible in this picture beneath the silencer. The expansion vessel slows down the speed of the exhaust gas due to it's large volume, but the entry pipe is horizontal and sideways displaced so the exhaust spins round the vessell droping its water content on the walls of the vessel. The water then runs out of a small drain hole at the bottom of the vessel. |
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Here's the fuel tank - a standard IBC. Unfortunately it could not be mounted heigh enough to operate as a gravity fed supply. This means we had to add a lift pump. We chose a solid-state facit pump as this gave us an adequate flow rate and pressure. However, the pressure (~6psi) was too great for the return pipe from the fuel injector to handle, so we made a mess of the engine room floor one night. It was fixed very quickly with a more robust return pipe. | |
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And here's another picture of the Volvox Combined Heat and Power system. | |
