Leaner and cleaner heating and cooling

Energy-efficient heating and cooling systems and renewables to cut consumption

By Morand Fachot

The building sector accounts for more than 35% of the world’s total energy demand, "of which 75% is for space heating and domestic water heating", according to the IEA (International Energy Agency). Heating is still mainly provided by burning fossil fuels, whereas cooling and ventilation systems rely primarily on electricity – the production of which is also largely reliant on the burning of these same non-renewable resources. Renewable energies are set to play a growing role in the heating and cooling of buildings as all countries try to cut their dependence on fossil fuels. A number of IEC TCs (Technical Committees) and SCs (Subcommittees) are involved in the preparation of International Standards for components and systems used in heating, cooling and ventilation installations.

CHP (combined heat power) boiler (Photo: Bosch) CHP (combined heat power) boiler (Photo: Bosch)

No end in sight to demand

Worldwide energy demand for the building sector is projected to grow by more than 60% between 2007 and 2050. A significant share of this requirement will come from heating and cooling applications, with the latter expanding more rapidly from 2030 onwards, driven both by income growth and climate change.

In Europe, the final energy demand for heating and cooling (49%) is higher than the figures for electricity (20%) or transport (31%). Cooling, ventilation and refrigeration account for roughly 20% of the overall electricity consumption of a building, obviously depending on climate and geographic location.

Reducing energy consumption for both heating and cooling buildings is an important factor in slashing the world's global energy demand.

Keeping heating and cooling demands under control

Cutting the energy consumption of buildings involves a variety of systems and actions. For machinery – such as lifts or escalators – and lighting, this can be achieved by installing more efficient motors and equipment as well as sensors, smart switches and energy-efficient light bulbs and appliances.

Reducing overall energy usage for heating and cooling is more complex, as it involves the building envelope itself as well as a number of other elements such as insulation and orientation. While cutting energy consumption for heating and cooling can be achieved fairly easily for new constructions, it can be complicated to adapt or retrofit existing building stock.

Introducing systems such as CHP (combined heat and power) and thermal energy storage and increasing the share of renewables like solar thermal will help cut the use of fossil fuel sources for heating and cooling and mitigate the impact of the anticipated increase in energy demand from the sector.

Rethink, new approaches needed

Heating and cooling requirements are obviously highly variable. In North America, for instance, heating needs are minimal or practically non-existent in southern states but cooling is required during many months of the year, while the opposite applies for northern regions of the continent. These distinct needs call for different systems or ones that can meet both requirements.

Heat pumps offer an interesting solution when both heating and cooling are required. They extract or add heat mechanically to a temperature source from the air, the ground or a circulating water loop within a building. In heating mode, they add heat into the building’s pipework systems from a source such as a boiler. In cooling mode they reject heat through a cooling tower or a fluid cooler, in the same way as a refrigerator does.

Heat pumps use external sources of power (electricity or fossil fuel), but are very efficient as they can supply as much as three times the energy that they consume. They can also be used all year round, providing both heating and cooling. This means that they can contribute to cuts in CO2emissions. According to the UIE (International Union for Electricity Applications), "The potential forCO2 emissions reductions via residential, commercial and industrial heat pumps is about 6% of global emissions. This is one of the largest savings that a single technology can offer". .

When heating is not needed

In hot climates, where a heat pump’s warming ability would be little used each year, AC (air conditioning) systems can offer a viable alternative. AC installations may be central units that use ductwork to transfer cooled air to and from various locations in a building, or standalone appliances installed in different parts/rooms of a building.

The latter are good for houses without existing ductwork and cheaper to install than central AC. They allow temperature levels to be adjusted for each room but have high maintenance and running costs and are expensive to buy.

IEC SC 61D: Appliances for air-conditioning for household and similar purposes, prepares International Standards for electrical heat pumps, air conditioners and dehumidifiers.

Additional solutions

Heating and cooling buildings can be achieved using a variety of other methods such as CHP and thermal energy storage. CHP, or co-generation, produces electricity and hot water or steam simultaneously from the same power source. This method could, theoretically, allow fuel to be used to almost 100% efficiency.

As part of its activities, IEC TC 105: Fuel cell technologies, "prepares International Standards for stationary fuel cell systems, especially for distributed small power generators and CHP systems". The IEC SMB (Standardization Management Board) has allocated to IEC TC 5: Steam turbines, the task of carrying out a study of standardization needs on CHP. IEC TC 5 will establish a relevant group that will liaise with TC 105 on CHP.

Thermal energy storage systems use a variety of means to store available heat in an insulated repository for use later in a number of industrial and residential applications, such as space heating or cooling, hot water production or electricity generation. One of the best-known and most widespread thermal energy storage systems is the domestic hot water tank. Other more efficient solutions may use salts or oils.

Thermal energy storage, used in conjunction with solar thermal systems, overcomes the disparity between demand for and supply of thermal energy and is thus important for the integration of renewable energy sources.

Renewable energies enter the equation

Renewable energy sources – solar thermal in particular, but also geothermal – offer a promising opportunity to cut energy consumption for heating and cooling buildings. In solar thermal systems, solar radiation is collected and the resulting heat conveyed using the medium of heat transfer. It can be used directly – for example to heat swimming pools – or indirectly, through a heat exchanger, for applications such as space heating.

TC 82: Solar PV (photovoltaic) energy systems, prepares standards for systems employing PV modules, which is true of most solar thermal systems designed for heating and cooling. 
Geothermal heating and cooling uses the energy stored as heat beneath the earth’s surface. It is currently provided in two different ways:

  • At depths of up to 400 m, groundwater and ground temperatures are low and fairly stable – up to 25°C. Heat pumps are used to raise the temperature to the level required by the hot water, heating or cooling application
  • At greater depths, where temperatures are between 25 and 150°C, heat extracted from the ground and groundwater can be supplied to a district heating network or to a CHP installation, or to drive local heat pumps to provide cooling to a cooling network

IEC TC 5 and SC 61D prepare International Standards for turbines and heat pumps used in solar thermal and geothermal energy systems.

The future will be more energy efficient and cleaner

As heating and cooling equipment moves away from its current heavy reliance on fossil fuels to cleaner technologies and renewable energies, significant energy savings and cuts in greenhouse gas emissions can be expected. Forecasts from a number of agencies and organizations assume significant technological advances in many systems (e.g. higher-efficiency components for heating and cooling systems, heat pumps, etc.)

While predicting future energy consumption patterns is an uncertain exercise, a European Technology Platform on Renewable Heating and Cooling report suggests that solar thermal alone could meet 3,6% of total European low-temperature heat demand in 2020, 15% in 2030 and 47% in 2050.

The IEA's Technology Roadmap: Energy-efficient Buildings: Heating and Cooling Equipment projects that 63% of the energy savings achievable in the residential and service building sector by 2050 could come from space heating, cooling and ventilation and water heating.
Other renewable energy sources such as wind power and concentrated solar power will provide the building sector with alternative and cleaner sources of energy. Heat pumps will also contribute as they become more efficient and are connected to renewable sources.

Whatever the eventual savings might be, the IEC will have made a major contribution to improving the energy efficiency of the building sector, and of its heating and cooling equipment in particular. The work of many of its TCs and SCs and the strategy papers that identify principal and emerging technological trends and challenges, and the means to address them, will help manufacturers and legislators find the best solutions in the developing marketplace.

CHP (combined heat power) boiler (Photo: Bosch) CHP (combined heat power) boiler (Photo: Bosch)
Air conditinuing unit (Photo: Sanyo) Air conditinuing unit (Photo: Sanyo)
Renewable energies are set to play a growing role in energy supply (Source: DuPont) Renewable energies are set to play a growing role in energy supply (Source: DuPont)