The basic premise of the Ecotherm concept is that for a part of each day and for a good portion of the year the heating and cooling demands of a building overlap i.e. parts of the building require cooling and parts of the building require heating at the same time. EcothermThere is therefore an opportunity to move heat around the building during these periods of overlap at very little cost. With traditional systems the excess heat removed by the
system is simply rejected to the outside of the building and is lost.
With Ecotherm this heat is recovered and reused.
The Ecotherm system uses refrigeration plant to provide both hot water for heating and chilled water for air-conditioning simultaneously. This water is piped around the building to air handling units via a four pipe network. The heat which is extracted from the chilled water along with the electrical energy used to drive the refrigeration compressor is transferred to the heating water. In this way energy is harvested from the warmer parts of the building and transferred to the colder parts of the building requiring heating.
When more heating is required than can be harvested from the building, the Ecotherm system absorbs heat from the outside air using a two stage evaporator coil. Up to 4 kW of heat can be gathered in this way for each 1 kW of electrical energy expended. This coil is fitted with embedded electric defrost elements. The coil staging and defrost elements are managed to ensure that ice does not build up on the coil and impede heat absorbtion.
Unlike other systems there is no reversing of the refrigeration cycle involved in the defrost process. Reversing the cycle essentially removes heat from the occupied spaces to melt ice on the outdoor coil which can cause cold drafts. Ecotherm however, is able to provide continuous heating.
When excess heat is being generated in the building this heat is rejected to the outside air using a dry cooling coil. Heating water is passed through this coil and fans are used to draw air through the coil and dissipate the excess heat.
The building is supplied with a fixed quantity of fresh air to ensure that the occupants remain healthy. An equal quantity of stale air is removed from the building via the toilets, photocopying rooms and other general points. As this air is extracted from the building it passes over a cooling coil which recovers a significant amount of energy from it. This energy is then recycled for heating the building or ventilation air stream again. The energy recovered in this way is sufficient to heat between 50 & 100% of the ventilation air stream depending on the outdoor air temperature.
Air handling units
The Ecotherm system utilises fan coil units with a single coil to service each zone of the building. Each fan coil unit is fitted with a changeover valve to enable selection of either heating or cooling water. A modulating valve for each service is used to control the amount of water flow through each fan coil unit according to demand. Local wall mounted sensors indicate room temperature, provide a night over-ride button and allow for local setpoint adjustment. The simple user interface is considered very important to the success and acceptance of the system.
Building management system
The Ecotherm plant is controlled by a digital building management system. This allows the operation of the plant to be controlled with a software program which provides enormous flexibility in the control of the plant and enables easy tuning and optimising of the system. Digital control enables a large range of variables to be monitored and used in the management of the system. The system can be remotely accessed via a modem.
Sensors are used to determine when partially utilized rooms are occupied and adjust the lighting and comfort levels accordingly. These sensors save lighting energy, heating and cooling energy, extend lamp or tube life, and can also be used as security sensors during unoccupied periods.
Ecotherm allows year round comfort levels to be achieved in a building in a most environmentally friendly way. There is no carbon dioxide generated by burning fossil fuels for heating. Energy is used in the most efficient way. Electrical energy used initially for running lights or computers is recycled for heating purposes when required. Water is used as the main heat transfer medium and there is only a small amount of HCFC refrigerant used in the refrigeration plant. This refrigerant is a small fraction of what would be required for a system using refrigerant as the principle heat transfer medium.
Ecotherm is an economical and ecologically sound approach to providing thermal comfort in buildings and promises to become the benchmark against which other systems are measured in the future.