|
contents | technologies | |||||||||
| New Flowable Fill for backfilling geothermal collectors  A modified cementitious and water absorbent Flowable Fill for constructing earth-touching and thermo-activatable building elements for geothermal storage & transfer purposes in ground source heat pump systems to establish centralised or decentralised underground mid- or long-term (seasonal) thermal storage units, and develop more efficient geothermal ground spaces right beneath or nearby-located to residential, industrial or commercial houses or buildings, – strong enough to be build over, environmentally friendly, maintenance-free, storage efficient and cost effective, long lasting, and corrosion resistant. And heat storage is the future key-technology for every modern energy-efficient district or unitary Green Building Design utilised preferred by alternative or renewable energy sources.Buildings of tomorrow require a combination of minimised onsite energy generation incorporating maximised renewable thermal energy sources, ultra-efficient building and insulation materials and equipment; waste heat recovery, and short-, mid-, and long-term thermal storage. Ultra-efficient building and super-insulation materials are necessary to reduce the general thermal energy demand and to make smaller thermal storage capacities possible. Narrow city right-of-ways and private land space is limited and growing expensive, so decentralised underground heat storage options are generally advised, which uses no open land or interior room space, and can be build over, and make the distance of transportation as short as possible. Those underground storage systems require less insulation, because they are covered by the particular building and embedded in the ground heat. Today, solar-thermal collectors are working quite well, but in order to make them more efficient, it is advised to run them with a short-term indoor storage tank in combination with a big enough outside underground mid-term storage unit, and long-term (seasonal) geothermal storage & transfer systems to maintain a sustainable and steady thermal energy supply all year round, that means also during nights and periods of cloudy, sunless days, and in the wintertime (seasonal use). So beside the solar energy the shallow ground heat is a high potential but low temperature renewable heat source with relatively low extraction values, into which other environmental heat sources, like the waste heat from untreated wastewater collection systems, low temperature heating & cooling systems like floor/wall/ceiling heating & cooling systems, and air-conditioning, and the heat from biomass boilers or micro-cogeneration and heat pumps also can be buffered. A heat pump is necessary to raise the relatively low geothermal heat temperature to a comfortable heating & cooling temperature level. And to charge and extract the heat or cold to/from the shallow underground commonly horizontal or vertical heat pipe exchanger are used, like horizontal-loop exchanger, trench collectors, and horizontal or vertical spiral collectors, also called "Slinky" collectors, installed not deeper than approx. 20 feet (6 m) into the ground. These devices are conventionally embedded into granular fill resp. in a sand layer, or fine excavation material from the same site. Compacting by vibration is not advised in this case because the collector pipes might be get damaged. So mostly backfill compacting by water and careful tamping by hand is used with more or less success regarding later surface settlements after the water seeps away and the backfill dries up and keep holes left. However, very important in this concern is, that maximum heat charging & extraction values can only be reached during later operation, if the backfill is always in firm connection to the collector pipes and as much as possible enriched with water. Because as is well known, that water saturated sand has a 4-part higher specific heat extraction output than dry, non-cohesive soil. Only from a few projects we know that also or Flowable Fill was used yet, especially for to embed horizontal collector pipes into foundation sub-bases, or for to backfill low-strength energy piles. But in all cases the ground under closed building infrastructures, including the backfill, is mostly more or less dry depending on the groundwater level, and therefore less well-conditioned for heat charge and extraction. Flowable Fill is a relatively new self-compacting, self-leveling, low strength concrete material, also called "Controlled Low Strength Material (CLSM)", with an adjustable flowable consistency, used as an economical fill or backfill material as an alternative to compacted granular fill. write your comments about the article :: © 2009 Construction News :: home page |