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Global Futures Report 2013 - Figure 4

28 n Solar Cooling Experts pointed to solar cooling as a key future trend. Solar cooling involves the use of solar thermal systems to drive chillers for air conditioning and other cooling needs, often integrated with conven- tional cooling systems. However, experts claimed that solar cooling is most practical for new construction, as it is much easier to inte- grate with cooling systems when installing in new buildings, rather than when retrofitting existing buildings. Solar thermal-driven chillers have traditionally been used only in large buildings, but one expert suggested that much smaller solar chillers could be designed that would be competitive in residential homes, if designs could be fashioned with much lower costs and lower technical complexity.36 One of the key issues that solar thermal experts discussed was how to take integrated approaches to managing power, heating, and cooling together in buildings. They explained that in many climates, the electricity summer peak is driven by cooling, so renewable cool- ing can help shave electric peaks. And heating and cooling are con- nected because solar thermal systems that are sized for adequate heat supply in winter conditions are oversized for summer use, so excess capacity can be used for cooling in summer.37 n District Heating District heating using renewables is already widespread in many countries. In Northern Europe, many countries make extensive use of biomass in district heating systems. Many industry experts and scenarios project growing use of district heating to efficiently supply clusters of buildings and whole neighborhoods, fed from biomass (either heat-only or combined heat and power), geothermal, and to a growing extent, large-scale solar thermal systems. Greenpeace notesthat,“thelackofdistrictheatingnetworksisaseverestructural barrier to the large scale utilization of geothermal and solar thermal energy as well as the lack of specific renewable heating policy.”38 (See also district heating in Chapter 4.) n Low-Energy or “Passive” Buildings Passive buildings are those with zero or minimal energy require- ments for heating and cooling, due to highly insulated building envelopes with low thermal loss. The concept of a passive building also encompasses high-efficiency heating equipment, passive solar architecture for solar gains, solar day-lighting, and embedded ther- mal storage. European experts noted that passive buildings will be key to the 2010 EU directive for “nearly” carbon-neutral buildings by 2018–2020.39 With a passive house design, small amounts of renewable heating and cooling are sufficient to provide normal comfort levels in all sea- sons. A biomass pellet stove, and/or solar thermal system in suitable climates, can then provide most of the required heating energy for all-season comfort, perhaps with a gas boiler or electric heat pump as back-up. For groups of passive houses clustered close together, a shared solar thermal system or district heating system of relatively small size can be used as a community energy system because of the low heat demand. One passive building expert thought that such buildings would emerge as a strong trend by 2020—leading to a “passive house revolution”—due to a confluence of factors, including the EU directive, new building products, new thermal stor- age components, economies of scale in manufacturing, consumer awareness, and integration into architect/engineer training.40 RENEWABLES GLOBAL FUTURES REPORT 02 INTEGRATED FUTURES: CHALLENGES AND POSSIBILITIES Figure 4: Buildings: Integration Opportunities 1 Two-way power flow with electric grid 2 Electric vehicle with battery used by house 3 Home energy management system 4 Solar PV panels 5 Solar thermal panels (heat and hot water) 6 Geothermal heat pump and hot water tank 7 Biomass pellet stove 8 Passive heat storage

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