Research shows that by installing smart systems into buildings there can be large annual savings, says Jonathan Allcock:

Abstract

The global energy system is undergoing a massive change due to an overwhelming amount of evidence relating to climate change; in order to continue to reduce carbon emissions and increase overall energy efficiency, it is important to look at where and how the energy is consumed. Buildings are the largest energy consumer by sector and account for over one-third of global final energy consumption [1], it is important to recognise this because it shows a need for intelligent energy management within the building sector in order to decrease carbon emissions, increase building energy efficiency and energy security.

Intelligent buildings contain systems that are able to adapt to their environment in real time, for example, space heating and hot water account for 60% of global energy consumption in buildings [1]. Therefore by installing smart controllers that are able to closely follow the demand it is possible to reduce total energy consumption and carbon emissions.

The research shows that by installing smart systems into buildings there can be large annual savings, for example, the University of Aberdeen estimates that leaving a 10kW furnace on 24hrs when it is not needed costs £29 while leaving 20 windows open during the heating season costs for £388 [2]. From this, it can be seen that there is large energy saving potentials to decrease carbon emissions, increase overall energy efficiency and improve building energy security by installing smart systems that are able to control every aspect of a building’s energy consumption as well as distributed generation sources such as solar, wind and cogeneration systems.

Introduction / Literature Review

An intelligent building as defined by the European Intelligent Building Group “creates an environment which maximises the effectiveness of the building occupants while at the same time enabling efficient management of resources with minimum lifetime costs of hardware and facilities” [3]. Focusing on building energy management it should be noted that there are two fundamental areas that should be considered, these are electricity and natural gas. The reason for this is outlined in figure 1 below:

Figure 1: Domestic Consumption by fuel (MToe), UK (2014) [4]

Figure 1 demonstrates the average energy consumption by fuel for a domestic dwelling, therefore it can be seen that natural gas and electricity make up 87% of total consumption with petroleum, bioenergy / waste and solid fuels contributing the remaining 13%. This is important because it identifies areas where large financial savings can be made, examples of systems that can reduce annual natural gas / electricity bills include intelligent boiler controllers, mechanical ventilation and heat recovery (MVHR) and autonomous lighting control systems.

Space Heating & Hot Water

Space heating and hot water production in a domestic building contributes 60% of its total energy consumption [1], it is important to recognise this because it shows that by performing small changes to the way the system is used it could result in large financial savings. The two most common ways of heating a home are through boiler systems i.e. hot water radiators and forced air systems i.e. HVAC systems. There are three types of boiler system commonly used, these are open vented, unvented and instantaneous [5]; while the energy savings measures are independent of the type chosen it is important to recognise which system applies and understand its operating characteristics. Unvented systems are much more complex than an open vented system because they allow for near mains water pressure and fewer components making it a more compact system.  Figure 2 below demonstrates a typical unvented hot water radiator system:

Figure 2: Unvented how water system diagram [5]

It should be noted that one of the most common problems that exist in radiator systems is unwanted air in the system; because of this, it is necessary to periodically go around each radiator and bleed the system of any air [6].

The second most popular type of heating system that is used for domestic space heating and hot water production is forced air. Forced air systems are driven by furnaces and are very different from conventional hot water boiler systems, for example, natural gas forced air systems to rely on air rather than water as the heat transfer medium. There are two main types of furnaces used, these are single and dual stage; the difference between the two is the fuel supply valve, for single stage furnaces the fuel supply has two positions, normally open and normally closed. Multi-stage / dual-stage furnaces are slightly different to single stage in which the fuel supply valve allows for normally open, partially closed and normally closed [7]. It is important to recognise this because it adds a new level to a furnaces’ operating characteristics, by including a third operating condition the furnace can run at a lower output thereby saving fuel and lowering its annual operating cost. Figure 3 below demonstrates the main components of a forced air system:

Figure 3: Domestic natural gas furnace for forced air heating systems [8]

When discussing furnaces / boilers it is important to be able to quantify their energy efficiency. In order to do this, a parameter Annual Fuel Utilization Efficiency (AFUE) is defined. AFUE is a measure of how efficient the appliance is in converting the energy in its fuel to heat over the course of a typical year; more significantly it is a ratio between annual heat output and annual fuel energy consumed, for example an AFUE of 95% means that 95% of the fuel consumed by the boiler / furnace is converted into heat for the building while the remaining 5% escapes to atmosphere (it should be noted that AFUE does not account for heat loss in the heat distribution system which could be as high as 35%) [6]. Figure 4 below demonstrates the relationship between AFUE and direct energy savings:

Figure 4: Higher AFUE Equals Greater Energy Savings [9]

It is also important to note that AFUE does not compare different types of systems, for example, it is not used to compare a natural gas furnace with an electric instantaneous furnace; rather it is used to compare a 90% AFUE Lennox propane furnace with an 85% AFUE Carrier propane furnace [9]. The reason that AFUE cannot be used to compare systems with different fuel type is because fuel choice is one of the largest impact factors when looking at how to reduce your annual fuel bill. For example, an electrical baseboard heater has an AFUE of 100% but a natural gas furnace with an AFUE of 90% will be much cheaper to run. Figure 5 below demonstrates this:

Figure 5: Cost comparison for 1 Million BTUs by fuel type [9]

Intelligent Control of Boiler / Furnace Heating Systems

There are many different ways to improve the overall efficiency of either a boiler hot water radiator or furnace forced air heating system. Two of the most common ways to do this are to implement a SMART boiler / furnace control system such as HIVE / NEST and to employ a method called ‘zoning’. Zoning allows more control over which radiator / damper is being used in what room, for example, if everybody is in the lounge then the heating in other areas of the house can by switched off / reduced i.e. kitchen, bathroom can be switched off to save energy.

Firstly looking at intelligent boiler controls it can be seen that systems such as HIVE, NEST, LOXONE etc. are smart controllers that give you more visibility over how you use your energy and proposes changes to actively reduce your energy usage. This can help to increase overall energy efficiency, decrease annual fuel bills and reduce the total carbon footprint of the building.

Taking NEST as an example it is easy to see why these types of intelligent boiler controls are able to reduce your annual fuel bill, for example, NEST learns how long it takes to heat your home from 18C to 22C showing that by turning the temperature to 27C will not heat the house any faster [10]. This is particularly important because the controller can also be integrated with real-time weather data allowing the system to auto-correct ensuring that the home is maintained at the desired temperature no matter the weather. One of the main benefits of NEST is that it is able to ‘see’ if people are in the home and set your boiler into auto-away mode further reducing total energy consumption; one of the ways it does this is by using 150⁰ wide-angle sensors or using your smartphone to detect your location, this is an interesting addition to an intelligent boiler control system because it allows the system to see where you are and adjust the temperature of your home, for example, if you are 1 mile away it will begin to heat your home such that when you arrive it will be at the desired temperature [10]. Figure 6 demonstrates the NEST device and its ability to integrate with real-time weather data:

Figure 6: NEST device with real-time weather data integration [10]

Another feature that is available with intelligent boiler control is the ability to control them through your smartphone, for example, NEST allows the independent control of central and hot water heating as well as scheduling i.e. 20C in a morning, 18C in the afternoon, 22C in an evening. This type of control is important because you do not always need to produce hot water thus saving energy that would otherwise be wasted on producing both hot water for the central heating and hot water for showers / baths etc. [10]. Figure 7 shows a typical interface a smartphone user would see when using systems such as NEST:

Figure 7: Smartphone interface for intelligent boiler control systems [10]

By giving the user increased visibility and easy controls they are able to see where they are able to identify cost saving opportunities i.e. turning off the boiler when nobody is home or reducing the temperature in the kitchen if everybody is in sat in the lounge etc.

The second method that can be used to improve energy efficiency is to create ‘zones’ throughout a building, this process is known as zoning. Zoning allows the user to isolate rooms of a building from one another (given that there is sufficient insulation between the rooms to prevent large heat leakage) allowing the user to individually set temperatures throughout their dwelling. This concept is important because according to the Energy Saving Trust by installing programmable thermostats and thermostatic radiator valves (TRVs) it could save in between £75 – £155 per year while turning down the temperature by 1C can save between £80 – £85 [11].

The type of heating system used i.e. hot water radiators or forced air slightly changes the device used for zone control, for example, if hot water radiators are being used then TRVs are installed to each individual radiator to control the flow of water thereby changing the heat dissipated from them. However with forced air systems dampers are used to control where the hot air is distributed i.e. it makes sense to close the dampers on the upper levels and pump the hot air from the lower level so as the air rises it dissipates its heat evenly throughout the building before falling back to the lower levels where it is then recirculated back through the heating vents. Figure 8 demonstrates the principles of zoning:

Figure 8: Principles of Zoning [12]

Building Electrical Infrastructure

Electricity is the second largest contributor to overall building consumption at 25% after natural gas 62%, figure 9 below shows the electricity breakdown for residential buildings in the UK:

Figure 9: Relative contribution from the different loads – All days – All households – With additional electric heating [13]

Looking at figure 9 it is possible to see typical electricity consumption in an average UK residential building, it can be seen that electrical heating, cold appliances, lighting, cooking and washing / drying constitute 68% of total electrical consumption while activities such as ICT and water heating contribute 8% [13]. The Department of Energy and Climate Change (DECC) produced a report looking at energy consumption in the UK, figures 10 and 11 outline their findings in regards to domestic residential energy consumption, if these figures are compared with one another it is possible to see that electrical consumption in all areas has increased however total energy consumption per person has decreased. This relationship is interesting because it shows that the energy efficiency of each individual appliance is having a great effect on overall energy consumption per person.

Figure 10: Domestic sector energy consumption per head and by income between 1970 and 2014 [4]

Figure 11: Electricity consumption by household domestic appliance, by broad type, UK (1970 to 2014) [4]

Smart Control of Electrical Appliances

Smart Meters

While individual appliances have improved energy efficiency it is also important to bring them together into a ‘smart network’, this allows for the optimisation of each appliance as well as further energy savings. There are many systems in the market that allow users to manage their electrical consumption such as smart plugs, LED lighting and energy management software which allow the user to gain more visibility over where they are using their energy and what steps they can take to reduce their total consumption and annual fuel bill. Taking intelligent devices such as smart plugs and smart meters it is possible for users to see what they are spending, know how much electricity they are using in near real-time and control individual devices from their smartphone i.e. turn lights, stereo, garage door on and off remotely [14]. Smart meters are an ideal way to convey complex information to users because they break it down into simple easy to read numbers, for example, it shows hourly and daily electricity / gas consumption and their attributed costs. This is important because rather than receiving one monthly bill users are now able to track their hourly energy consumption and adjust their habits accordingly so there are no surprises when their monthly bill arrives. Figure 12 below demonstrates how smart meters work:

Figure 12: How smart meters work [15]

Smart meters are particularly important because they help to show users specifically how many independent tasks cost them, for example, how much does it cost to leave the heating on all night rather than switching it off between midnight and 4AM? These types of analytics are important because it helps to kerb the inefficient or high energy consumption habits thus reducing the load on the electricity / gas network, this concept is also known as ‘demand response’.

Building Automation Systems

While there are intelligent controllers in the market to individually manage heating and electrical systems it is more efficient and user-friendly to combine the two and have one centralised system that can manage everything from building security to the integration and optimisation of renewable energy systems such as photovoltaics, wind etc. Building automation systems and centralised packages that are able to control a multiple of different systems, for example, blinds, lighting, multi-zone heating, multi-room audio, energy and security. Figure 13 demonstrates a typical intelligent smart residential building and its components:

Figure 13: SMART home component breakdown [16]

Figure 13 shows that there is an array of sensors gathering information across a variety of different areas, for example, sun intensity, wind speed, temperature, humidity etc. Because the system is constantly assessing the interior and exterior conditions it is able to react, an example of this is automated blinds that are able to open and close to maximise the thermal energy from the sun. This is important because by adjusting the height of the blinds it is possible to assist the buildings’ heating / cooling systems during the winter / summer months thereby reducing total energy consumption, annual fuel bill and carbon emissions. Figure 14 demonstrates the operating principle of intelligent shading:

Figure 14: How does intelligent shading work? [17]

In addition to intelligent shading building automation systems are able to manage an array of other systems, for example by installing multi-zone heating control it is possible to save up to 33% (£400 off an average dual fuel bill of £1385) on your heating bill [18]. Multi-zone heating is a technique of installing multiple thermostats throughout a building to create ‘zones’, by creating areas that are individually temperature controlled it ensures that the building is only heated when it needs to be thereby maximising operational efficiency [18]. One added benefit of smart heating is that the user is able to define an operating schedule based on their weekly activities, because of this the building management system is able to adjust / maintain each zone at the desired temperature ensuring that the building is maximising its total energy consumption.

When creating individual zones in a building it is important to ensure that each zone is properly insulated from the next to reduce heat leakage from one zone to another. In order to control the heat output per room, adjustable radiator valves are installed to manipulate the flow of hot water through the radiator.  Figure 15 below demonstrates the principle of zoning:

Figure 15: Multi-zone heating and how it works [18]

Integration and Optimisation of Renewable Energy Systems

Intelligent buildings not only include the management of internal systems such as heating, cooling and power but can also include the integration / optimisation of renewable energy systems such as photovoltaic and wind. By successfully integrating renewable energy sources into a building’s centralised intelligent control system it is possible to maximise their use. For example energy intensive appliances such as dishwashers, dryers and washers can be configured to run when there is sufficient power being generated from the renewable system [19]. This type of optimisation is important because it allows the user to maximise their benefit from government schemes such as the Feed-In-Tariff (FIT) while also benefiting from a reduced electricity bill.

By integrating external energy sources into central building management systems it is possible to connect different processes together thus improving overall energy efficiency and reducing annual fuel bills. One example of this is if a building has a solar thermal and conventional natural gas heating system it is possible to configure the controller such that the hot water can be produced by the solar thermal system on the roof rather than using the conventional natural gas system. Figure 16 shows the integration of multiple energy sources and energy storage options:

Figure 16: The integration and optimisation of renewable energy systems [20]

Looking at figure 16 it can be seen that many different types of renewable energy technologies can be integrated such as heat pumps and small wind. However, it is also important to recognise that there other emerging technologies that are affecting the energy market, one example of this is the electric vehicle.

Electric Vehicles and Their Effect on Smart Buildings

Electric vehicles are having a significant on the global energy system and their role is not limited to an alternate mode of transport, one research method involves using the car as both buffers and temporary storage units when connected to buildings. The principle of this is fairly simple, for example when an employee drives to work and plug their vehicle into the base charging station the building recognizes this, if the weather suddenly becomes cloudy and the PV system on the roof is unable to meet the required demand the stored electricity in the vehicle can be used to offset the gap and compensate for the reduced output [21]. However on the reverse side if the PV system is generating too much power then the excess can be syphoned off and directed to the charging station thereby storing the excess electricity in the car’s batteries. This is important because if buildings were to forecast their energy consumption and send it to the grid operator, then they could provide a fixed price i.e. 100MWh = £140. This methodology defined as the ‘Internet of Energy’ by Siemens is very interesting because electric cars could be used to stabilise the energy consumption of buildings making it easier for the grid operator to forecast the total electrical demand [21].

The role of smart buildings in smart cities

One of the more interesting applications of intelligent buildings is their role within smart cities; smart cities are defined by the European Commission as,

“places where the traditional networks and services are made more efficiency with the use of digital and telecommunication technologies, for the benefit of its inhabitants and businesses. However this concept is not limited to improved energy and resource management and reduced carbon management, it also includes smarter urban transport network, upgraded water supplies and waste disposal facilities and more efficiency ways to light and heat buildings [22]”.

This definition is important because it shows how stand-alone intelligent buildings can be connected to one another to form a smart network which is able to communicate and manage its energy in a positive and efficient way, figure 17 below demonstrates a concept for a self-contained smart city:

Figure 17: Demonstration of a future self-contained smart city [23]

Looking at figure 17 it can be seen that smart cities are very complex and have a multiple of variables to contend with i.e. various distributed generation sites, energy storage as well as different types of energy consumers. However there are many reasons that the smart city concept should be adopted, the top three are the seamless and instantaneous sharing of information, they are less intrusive and they have shorter processing times and higher / faster reactions times meaning they can react to changes in energy demand, environmental conditions etc. As a result of this smarter buildings / cities are needed to improve overall energy efficiency, reduce our global carbon footprint and maximise each and every energy saving opportunity.

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Jonathan is an energy engineer with a passion for SMART buildings and their role in a low carbon economy. He is also the founder and Director of “Energy Innovators”, a start-up company supported by the Princes Trust to provide energy consultancy and state-of-the-art aerial thermography / inspection for commercial and industrial customers’.

He spent 10 years living in Toronto where he graduated with a BEng(Hons) Energy Systems Engineering in 2014 before moving back to the UK to complete an MSc Energy Systems and Thermal Processes at Cranfield University in 2015.

Jonathan’s current research areas include intelligent buildings, low carbon transport solutions and real-time 3D thermal modelling.

Contact: jonathan.allcock1@gmail.com