The Continental Ferry Terminal in Portsmouth is currently being remodelled, and a new passenger terminal building is being designed with the aim of reducing energy demand and CO2 emissions by utilising sustainable features. The building is being designed to achieve a minimum BREEAM rating of “very good”, with the aspiration of achieving “excellent”.
The first priority for designers was maximising the benefit of the climatic setting of the building by adding a series of passive measures. The form, orientation and building envelope itself are designed to exploit natural daylight and to capitalise on diurnal and seasonal variations in temperature. In order to minimise the need for mechanical cooling, passive cooling measures will be employed. These measures will include the use of exposed thermal mass and a night time ventilation strategy with automatic controls.
In order to further minimise the need for mechanical ventilation, natural ventilation systems will be harnessed. The problem of reduced air quality at the port, (due to the exhaust fumes from the numerous vehicles in close proximity to the terminal building), presents an opportunity to utilise roof-mounted ‘windcatchers’. Windcatcher terminals are designed to exploit wind pressures to both supply and extract air through the roof terminal, and are suited to the coastal location of the terminal, with its higher-than-average wind speeds.
A simple windcatcher consists of a square louvred turret that is separated diagonally into four quadrants. Whichever direction the wind blows, the two quadrants on the windward side will be at positive pressure and force fresh air down into the building. The two quadrants on the leeward side will be at negative pressure and thus drain stale air from the space.
Motorised dampers at the base of the vent are automatically controlled to adjust the air volume through the terminal according to temperature and/or carbon dioxide levels within the space. In the absence of any wind, the terminals will act as passive ventilators with warmer, more buoyant air rising from the space to escape through part of the terminal being replaced by cooler, denser air falling into the space through the other part of the terminal.
Sea water-source heat pump
It is feasible for a sea water-source heat pump to be installed, which could be used to provide the entire terminal’s heating and cooling year-round. In order to be economical, the heat pump will be matched to the terminal’s base load in order to ensure near-full output operation all year. The cooling load within the terminal is estimated to be around 130kW. A water-to-water heat pump is being considered, with sea water used as the heat sink to dissipate the excess heat from the building. If a reversible heat pump is installed, a similar amount of heat could be extracted from the sea to provide heating during the winter. Developers are proposing a closed loop system, where a heat exchanger will be fitted within the dock and a water/glycol solution circulated to the heat pump. This should minimise the on-going maintenance issues associated with the corrosive nature of sea water and possible biological growth on exposed parts which is associated with an open loop system (where sea water would be pumped to the heat pump unit within the building). The heat exchanger will be mounted on rails on the dock wall so that it can be raised above water level for inspection and cleaning.
The use of potable water will be minimised via the following water-saving technologies:
- dual flush low volume cisterns
- waterless urinals
- spray/aerating/time controlled wash basin taps
- flow restrictors
- leak detection
- occupancy controlled isolation valves
The use of sea water to flush WCs (and urinals, where not waterless) is under investigation. Sea water would need to be filtered and probably UV treated prior to storage in high level tank(s) and then would be gravity fed to individual WCs. The initial response from Southern Water’s Trade Effluent department has been positive as the likely volume of sea water entering the sewage system is not considered to be a problem. Similarly there is no objection in principle from the Environment Agency, and because of the annual water volume involved, it is unlikely that a permit will be required.
Page last updated: 18 August 2010