Eco buildings are often described as passive house buildings (Passivhaus is a german term). The term has evolved into an international standard that is used to describe, measure and certify any sort of building that consumes almost no energy to maintain its comfortable temperature.
Flitwick mill is effectively a timber-framed building plonked on the top of a single story brick structure. The difference between a modern timber frame building and an old one lies in two clearly identifiable assets. The quality and integrity of the insulation and the timber used in the construction.
The timbers of old buildings have lasted for many decades or centuries, those of modern houses are designed for a short life of 60 years. Those of Flitwick mill are already several centuries old and generally they are in excellent condition.
There is no insulation within the construction of Flitwick Mill. A factor that needs to be rectified and in practice this is easily achieved without compromising its appearance. It is important to pay exquisite attention to the detail of how this is done, even then it is unlikely that we will be able to achieve results approaching passive house standards. Windows and doorways need to be replaced with working examples that are fitted with suitable modern seals.
Water power is essentially a localised renewable source of energy. Mills use this energy to directly generate mechanical work for a myriad of activities from grinding flour to sawing timber and slate and for driving a large range of machinery in cotton and wooden industries. In the early days of milling, the power of water was harnessed with little harm to the surrounding envrionment. By the Victorian era, steam and electricity were increasingly being used to power mills. Modern thinking towards renewable energy effectively turns the situation full circle and it’s universally recognised that wasting that clean, simple, quiet form of energy is pure folly.
The amount of energy in a river is a function of flow and pressure (or height in the case of a waterwheel). These can easily be measured. In our case we have enough water energy to power two mill-stones and associated layshafts and auxiliary equipment in the mill.
In order to convert water energy into electrical energy we need a device that the water can do work on and a generator that converts the work into electrical energy. The effective options include a waterwheel, an archimedes screw or a turbine. Since we already have a serviceable waterwheel that the planners want us to restore and keep then we have to arrange for a suitable generator to be driven by it.
The simplest generators are essentially motors (that would normally drive machines) fitted with suitable electronics so that when they are driven mechanically they become electrical generators. The resulting electricity is either used in-house or sold to the electricity grid.
And there are snags. The waterwheel runs very slowly (10rpm) compared to a typical electric motor (1500rpm). This means it needs a 150:1 gearbox to drive the motor near to it's correct speed. Moreover it requires a very tough gearbox indeed to be able to transfer the turning power of a waterwheel into relatively high speed rotation of a standard electric motor. If it were 1KW it needs to handle 1kNm of torque and for 50Kw that number it a very dramatic 50kNm. This necessitates very big and strong bearings and couplings.
The alternative is to find an electrical machine that can be driven slowly by the waterwheel and that can handle to power generated. This is exactly what happens in wind turbines where modern generators run directly coupled to the propeller shaft. There is no gearbox. So gearbox reliability is 100% because there isn't one. We are currently investigation both of these options.