Active solar water heating

As described in Chapter 2, passive solar water heating systems have the merits of simplicity and are usually reliable. These benefits, however, come at a price. The systems are inflexible in that they need the hot water storage or heat exchanger to be positioned above the solar collectors, and they are difficult to integrate with other forms of alternative energy technologies. Water-based active solar water heating systems use pumps to circulate the heat collection fluid between solar collector...

Pyrolisation gasification and anaerobic digestion

Pyrolysis Process Making Charcoal

Even when a particular biomass material is suitable for straightforward burning as described in Chapter 7, this will not necessarily be the most efficient way of recovering the embodied energy of the biomass. Materials with naturally high moisture content in particular may well contain significant amounts of hydrocarbons and other organic materials but drying them to a state in which they could be fed directly into a boiler is rarely either practical or economic. However, alternative...

Active cooling options

Parabolic Trough Plant

Passive cooling systems, like passive space heating systems, have many attractive features, not least simplicity, cost and reliability. They also have serious limitations. Windcatchers, solar chimneys and the stack effect on their own can never ensure that stale warm air is always extracted from every nook and cranny of every building and that cool fresh air always replaces it at a rate which significantly improves occupant comfort. Larger buildings with complex floor plans that depend entirely...

Active solar space heating

Solar Heat Capture For Winter

Adding pumps or fans to passive solar water or air heating systems can greatly increase their overall efficiency and sophistication, at the expense of greater capital and running costs and lower reliability. Active solar space heating systems can take full advantage of thermal store possibilities to significantly reduce the need for back-up space heating. More solar heat can be utilised for longer periods, and extremes of temperature can be mitigated more effectively. Active solar water space...

Cogeneration trigeneration and beyond

Power Chp Buffer

Generating the electricity that the modern world depends on by burning hydrocarbons can be a very inefficient process. This is particularly the case where the electricity is generated in large power stations then transmitted long distances to the consumer. National electricity grids may be very convenient, for producer and consumer alike, but as little as one-third of the chemical energy in the fuels burned actually arrives in the form of electrical power. This applies to both fossil fuels and...

Smallscale hydropower

Pelton Shoot Head Penstock Forebay

In many ways hydropower is the ideal alternative energy source. Its delivery is much more reliable, consistent and predictable than wind or solar energy. Modern turbines can extract up to 90 of the kinetic and potential energy in the water that passes through them -although an overall efficiency of 70 is more typical for small installations. More power is usually available during the wet winter months than in the summer, a supply profile that more closely matches normal demand. Unlike some...

Passive solar space heating

Manual Operated Air Dampers Air Handlers

As global warming becomes more obvious, the need for space heating in most developed countries will decrease, even as the need for space cooling increases see Chapter 8 . Nevertheless, for many years to come the energy required to keep buildings comfortable for their occupants during the depths of winter will still be a sizeable fraction of the world's energy needs. In Europe currently this fraction is estimated at more than 12 . Even with enhanced standards for insulation and increasingly...

The Stornoway Waterwheel

Waterwheel Overshot System

A modern version of the classic overshot waterwheel is at the centre of an imaginative restoration project in the Outer Hebrides. Back in the early nineteenth century, the subsistence economy of western Scottish islands like Lewis was based on a plethora of small vertical axis or 'Norse' waterwheels. These powered the grindstones that ground the barley and oatmeal which formed the staple diet of the locals - wheat was unsuited to the infertile, acid soils and cool, damp climate of the Hebridean...

Passive cooling options

Courtyard Cross Ventilation Analysis

As the climate warms, the demand for environmental cooling will inevitably increase. It would increase anyway in developed countries the acceptable ' comfort zone' inside buildings is becoming narrower. Occupants are less and less willing to modify their clothing and habits in response to seasonal changes. Fifty years ago clerical staff thought nothing of wearing woollen underwear to the office, where men would work in three-piece suits, collar and tie for most of the year. In the height of...