When is natural ventilation the right solution for power plants?
Posted on Tue, Oct 18, 2011
The quick answer is: in most cases. Power plants generate large amounts of internal heat and tend to be in tall buildings, which present ideal conditions for natural ventilation to work at its most efficient.
Whether you are designing a power plant or rethinking how to achieve the right balance of temperature, humidity and air quality in your plant while keeping costs down, you will be looking at the respective benefits and feasibility of natural and mechanical ventilation.
As a designer, it is your responsibility to ensure that the ventilation systems you select guarantee the plant’s maximum temperature limits are never exceeded. These are the maximum temperatures that allow the efficient operation of the plant as well as comfortable working conditions for the staff.
What are the main factors that affect your plant’s internal climate?
• Excessive heat
• Excessive condensation
• Contaminants released by the power generation process
Why is natural ventilation the answer?
• Internal heat gains are very high compared to external ones, which results in a good temperature gradient through the building;
• Power plants are typically high structures, creating a good stack effect that makes moving air between different levels within the building easier;
• Natural ventilation will not only lower internal temperature very efficiently, but also reduce humidity and extract contaminants, creating a comfortable working environment with good air quality.
As a designer, you are also looking for a solution that is cost effective, and with natural ventilation running costs are negligible:
• No energy consumption
• Minimal maintenance
• Self-compensating: the hotter the air, the more air can be moved and the more efficient the system is.
• Long life span
• Not liable to breakdown
How can you determine which is the best solution?
Computational Fluid Dynamics (CFD) analysis, carried out by an expert in CFD simulation, is an excellent tool to identify the best system for each building. These simulations can show the flows and transfer of energy within the building in different situations, helping to develop the most effective solution.
Fig-1 shows a building with areas of different heights open to each other. In this building, the neutral plane is in the top section of the building, so the natural ventilation system only needs to provide extract in this area, while air inlets are spread at low level across all areas.
Fig-2 shows air movement and velocity within the building, indicating the best locations for inlet and extract ventilators.
When is natural ventilation not the answer for a power generation plant?
There are power plants where the building is not high enough to create a stack effect that enables a natural ventilation system to be effective. There are also plants where the turbine hall is enclosed within the main structure, so there is no direct access to the outside through an external roof.
In these cases, mechanical ventilation is the answer. We will see how this works and the benefits of this solution in a future post, so watch this space!
Image attribution: MF Robinson
Bradley Smith is a Business Development Manager at Colt UK with experience in the design and application of HVAC and smoke ventilation systems.
