A safe approach to converting waste
Every building brings its own challenges when it comes to ensuring it provides a comfortable and safe working environment. Internal conditions are determined by its shape and size, its thermal characteristics, the processes it houses and the uses made of different areas.
Energy-from-waste plants present particularly challenging conditions. These facilities produce heat energy through the combustion of waste. Electricity is generated using the steam created by the combustion process to drive a turbine.
The condensation from the steam and the intense heat generated by the turbines produce high levels of humidity and temperature that need to be addressed in order to achieve a comfortable environment.
The presence of large quantities of waste and the combustion process require efficient ventilation and filter systems to ensure good air quality within the facility and to prevent the dust, fumes and odour from escaping into the surrounding environment.
Dealing with excess heat
The first step in identifying the right solution is a review of the level of heat emitted from furnaces, ancillary process plant, lighting systems and solar gain. This data is used to calculate the heat load. This, plus the type and use of each building, will determine the amount of heating and ventilation required to achieve comfortable conditions.
There are three ways to remove heat and contaminants: natural or powered ventilation systems, or air conditioning.
Natural ventilation is the most cost-effective and energy efficient option, if it is practical. It harnesses the natural elements of heat and convection to move air through the building and using wind pressures externally to improve the air quality, often at a fraction of the capital, space and running costs of other methods.
Energy-from-waste plants require ventilation systems that can clear excessive heat and airborne dust. The need to create an escape route for extreme amounts of waste heat demands the use of industrial strength natural ventilators.
The Colt Labyrinth ventilator is an example of the type of roof equipment designed to meet these requirements. This is the system Colt installed in the furnace and turbine buildings at the Allington energy-from-waste plant in Maidstone, Kent.
The Colt Labyrinth system uses the natural buoyancy of warm air to discharge hot air and provides continuous, rainproof ventilation as well as acoustic attenuation. At the Allington plant, Colt also installed a system of fans and ventilation shafts that draw external air through louvres at the top of a shaft and distribute it throughout the building. Filters are installed in the ducts to deal with dust and odour.
For low level inlet Colt can offer their Universal Louvre range. These are single, double and triple bank louvre systems designed to meet the requirements of high efficiency ventilation with rain defence where required. All of these can be supplemented by acoustic louvres, filters, dampers and heater batteries.
Combining work spaces
Energy-from-waste facilities often combine plant and office spaces, which may include IT suites and meeting rooms. A different approach is required for the latter, where conditions are not as extreme as in the plant.
Depending on the structure and position of the building, a combination of natural ventilation and solar shading can be the best solution. Solar shading reduces additional solar heat gains while discreet façade dampers linked to internal CO and temperature sensors control the amount of air movement within the space.
In other cases, an air conditioning system may be required. Colt’s Caloris WRF system is highly energy efficient and offers individual control for each section of the building, addressing the issue of IT rooms requiring more cooling than office areas.
This system can make use of the building’s thermal mass, water reservoir or ground source installation as heat sink for heating and cooling. It is based on WRF (water and refrigerant flow) technology, which combines the advantages of VRF (variable refrigerant flow) and heat pump technologies within a safe, highly efficient water-based system.
The Colt Caloris WRF system can also use the heat generated by the energy-from-waste plant’s combustion process to heat the office areas. It can connect to the plant’s hot water system and distribute free warm air through the indoor heat pump units installed in the offices.
Integrating smoke control
In the case of fire, smoke is the greatest threat and can fill large areas very quickly. An effective smoke control system provides the building’s occupants with a clear escape path and allows fire fighters to enter the building earlier and tackle a fire at its source, increasing the chances of saving the building and its contents.
Smoke ventilation can be integrated with the natural ventilation system. For example, at the Allington energy-from-waste plant, Colt installed roof mounted smoke louvres throughout the plant, including the incinerator hall where they will contribute to the area’s natural ventilation system by providing air discharge for the cooling air.
Conversely, natural ventilation louvres can be integrated in the smoke ventilation system and come into play when needed to aid the extraction of smoke. This dual purpose system saves money and reduces the number of roof penetrations required.
Every facility is different and it pays to seek professional guidance to determine the specific requirements for each. An integrated approach at the design stage enables you to find the most effective solution, in terms of installation costs and performance, and this is especially true of waste-from-energy plants because of their peculiarities and challenging conditions.