Controls have a key role in reducing carbon emissions
Effective controls in existing buildings are an important feature if we are to meet the UK's challenging carbon emissions plan. George Adams shares his experiences.
As we move closer to the UK's carbon-reduction deadline, we are realising that much more has to be done to our existing buildings to be more efficient. Around 26 million domestic and non-domestic buildings equate to about 50% of our carbon emissions, so as engineers we will be called on more and more to economically reduce energy consumption and create long-term sustainability of our building stock. Since new buildings amount to only 1 to 2% of the building stock each year, they alone will clearly will not achieve anywhere near the carbon reductions of 80% by 2050.
Buildings have heating, lighting and, often, mechanical ventilation and cooling to create habitable spaces to work, socialise and live in. So upgrading existing controls is, in many cases, an effective opportunity for minimising energy use by the engineering systems in them.
Clients will require their new or upgraded controls system to contribute to energy saving, maintenance, and environmental needs — but with different degrees of the core drivers for each client’s needs.
Operating costs are increasing, and primary electrical energy costs are likely to rise by 30 to 50% over the next four to five years. Also, the UK is likely to be producing only 80% of its own electrical power within the next 10 years.
So CEOs and CFOs will become more concerned about cost increases and potential supply stability issues in the coming years. Improving or replacing control systems will be an important part of the strategy to deal with these issues.
In existing buildings some energy savings can be achieved by re-commissioning and adjusting existing controls. Improving controls is a viable option because current technology can often be retro-fitted into existing panels/systems which will often be basic and inflexible. However, some circumstances may require the existing system and panels to be completely replaced.
Surveys and operational checks often reveal existing systems to be in poor condition and have limited flexibility, with components failing. Documentation, drawings or the history of modifications can also be missing. The key tasks in assessing existing systems are as follows.
• Establish operational use of the facility, how it’s managed and how users relate to the engineering systems such as heating and the energy objectives.
• Inspect log books or help-desk reports for records that highlight operational issues.
• Review the energy consumption and produce a profile showing trends and any unusual spikes or patterns
• Identify the outgoing circuits so system diagrams can be produced.
• Obtain current loadings from each item of equipment fed from the existing panels.
• Logistics planning will be necessary for keeping the facility operational, conducting work in a safe method and to organise replacement equipment in a convenient way.
• Conduct system selection and life cycle studies of the options.
In refurbishment projects, items of plant will be found to be inefficient or not working. These will need to be identified and reported with recommendations to the client or owner.
Radio-based sensors can be used to great effect and save significant money in reducing new cabling for the control system and can be better located. There are new sensors with integral photocells to overcome the issue of battery replacement where sensors are in remote locations.
Basic control functions are a sensor, a controller and a device that is being controlled. The sensor collects information for the control system to respond to, so the selection and application of sensors is critical to achieving an effective solution. Sensors that are poorly located or suffer from control drift will affect both environmental comfort and energy consumption.
However, two or more such problems in control systems have cascade effects that affect the efficiency of the facility and wellbeing of occupants. Sensor selection and application is therefore of fundamental importance.
Engineering systems modify the climatic conditions and the internal environmental conditions, with the control system responsible for managing how engineering reacts to changing parameters. Controls have a fundamental role in the consumption of energy to allow this process to take place. Yet controls are also seen as an important part of energy-conservation measures. Controls therefore are critical to the efficient use of energy and achieving good internal environments for the wellbeing of occupants.
Controls also have a key role to play in the safe operation of the engineering systems and in the raising of alarms to identify problems to the maintenance or building management.
Hence, the level of control system sophistication arises in relation to the owner or occupier energy and operational policies.
There are basically five levels of control, which are listed in order of increasing cost and benefits.
• Local manual controls.
• Local automatic controls.
• Direct digital control (DDC).
• Building management system (BMS).
• Integrated control systems.
The services engineer must analyse the requirements and select the best-fit solution for the facility with regard to its operational needs, the planned maintenance regime and current legislation. The CIBSE and BSRIA provide good sources of publications to assist with making the best decisions.
The continuous development of technology and systems integration requires skilled engineering assessment in order to select the best solution for the client’s needs and constraints. The building-services engineer is important to lead the system selection to ensure the controls solution is related to the engineering systems, the building form and function and the wellbeing of the occupants. At all stages the controls application engineer and facility manager or maintenance manager must be involved in the decision making.
To encourage appropriate change it is necessary to consider all the aspects highlighted above. The economic life-cycle expectancy of the facility and its control system must identify the benefits of cost, carbon reduction, operational efficiency, environmental effectiveness and maintenance requirements and advantages.
However, when considering the advantages of upgrading or replacing the control system, the level of sophistication needed must be decided upon with the end users and their operational capabilities in mind.
Establishing an appropriate energy and operational policy for the facility and its users is critical to arriving at the best system selection and how to apply it. Hence, new policies should be established at the outset so that the parties involved are encouraged to consider all the aspects highlighted above.
George Adams is engineering director with SPIE Matthew Hall.
