Whether in the US or India, improvements to energy efficiency can often be attained through no-cost or low cost ECMs that lower the first costs of construction and equipment. Optimizing building loads can lead to lower first costs and operating costs. By targeting low-hanging fruit through early-stage ECMs, the first costs saved through these can be applied toward more expensive technology solutions like high-quality glazing or sensors that can further the energy and cost benefits later in the building life cycle. Hence, it is important to decide which measures to prioritize initially, and then what to cross-subsidize eventually. For example, if one is able to save costs by reducing the number of lighting fixtures and taking advantage of high daylight levels in a space, then those savings can be used to install daylight sensors. The latter can provide a large cost benefit with a relatively short payback time by driving down the operational hours for artificial lighting. The ECMs at the whole building level using systems integration can greatly benefit the EPI of a building. Table 1 shows whole building energy use metrics, using Standard , Better , and Best Practices at the whole building level.Displacement ventilation delivers the air at low speeds using the principle of air stratification. Here, air is delivered at close to floor level for primarily conditioning the occupied volume and extracted at the ceiling height rather than conditioning the unoccupied higher volume first.
Well designed DV systems provide better indoor air quality since the air in the occupied zone is generally fresher than that for mixing ventilation. There are no perceived air drafts. Any released pollutants rise rapidly to above the occupied zone. Large cooling energy savings are possible, as it uses a higher supply air temperature at 18°C,rolling bench which also increases the efficiency of mechanical cooling equipment and lowers equipment requirements. Underfloor Air Distribution technology uses the underfloor plenum beneath a raised floor to provide conditioned air through floor diffusers directly to the occupied zone. A thoughtful design can overcome the usually cited challenges of uneven floor surfaces, difficulty in providing added airflow to the perimeter of the building, and perceived control difficulty. The advantages of a well-designed UFAD system are: improved thermal comfort, occupant satisfaction, ventilation efficiency and indoor air quality, reduced energy use and the potential for reduced floor-to-floor height in new construction. Radiant Cooling works on the principle that water can store 3,400 times more thermal energy per unit volume than air. It offers the potential to reduce cooling energy consumption and peak cooling loads when coupled with building thermal mass. Some radiant systems circulate cool water in dedicated panels; others cool the building structure . Because radiant surfaces are often cooled only a few degrees below the desired indoor air temperature, there are many opportunities for innovative cooling energy sources, such as night cooling and ground-coupled hydronic loops. The heating and cooling supply water temperatures for radiant systems operate at higher set points compared to traditional systems.
The radiant cooling system supply water temperature would typically operate at 15°C–18°C for cooling, whereas typical supply water temperatures for a traditional forced air system are around 5.5°C–7.5°C. The central cooling equipment can operate more efficiently at these temperature set points.In a typical office space, the airflow required to cool and ventilate the space can be three to four times greater than that required to just ventilate the space. If the space cooling is decoupled from the ventilation, especially through a hydronic system, the central air handling system and associated distribution system can be downsized accordingly. A system called a Dedicated Outdoor Air System is typically used to serve the ventilation needs. A DOAS also allows for the effective use of energy recovery on the incoming outside air to further reduce the associated heating and cooling ventilation loads. Localized demand control ventilation can also be implemented to turn off the ventilation air when the space is not occupied, which further reduces the total system energy. The efficiency gain of this demand-control ventilation strategy needs to be weighed against the additional system complication, cost, and the additional fan energy necessary for the required air terminals. Also, the traditional air distribution system has air terminal devices to modulate the cooling capacity to each individual space. These air terminals add additional pressure drop and increase the associated fan energy. With a DOAS, the air terminals are not required for proper system operation. The space saved by using a DOAS can be used to install a low-static air-side distribution system to further reduce the associated fan energy. Therefore, consider decoupling the cooling and ventilation. Separate the process load and the regulated sensible load from the latent load . Serve different types of loads by various levels of cooling relevant to the specific need. Soil salinity adversely affects crop productivity and agricultural sustainability in many areas of the world, especially in arid and semi-arid regions .
Plant growth can be inhibited by high salt concentrations through osmotic stress, nutritional imbalance, and specific ion toxicity . It is known that the growth inhibition and the adverse effects induced by salinity can be alleviated by proper use of fertilizer and water management, depending on plant species, salinity level, and environmental conditions . Nonetheless, over fertilization with N may contribute to soil salinization and increase the negative effects of soil salinity on plant performance . In addition, the potential for NO3 leaching may increase where moderate to high amounts of salts are present in the soils because plants under salt stress can not absorb and or utilize the applied N as efficiently as the plants not subjected to salt stress . Further, as the salinity of irrigation water rises, the leaching fraction must increase to control root zone salinity. Higher leaching fractions combined with lower N use efficiencies represent a worst case with regard to groundwater pollution . Therefore, judicious fertilizer and water management is essential in salt-affected soils to sustain yields and to minimize the degradation of soil and groundwater. In the arid Xinjiang province of China,grow table hydroponic cotton is being grown widely because of its high salinity tolerance. In these regions, water sources are frequently brackish and high-quality water for agricultural purposes is increasingly scarce due to rising demands from urban areas . As a result, the proportion of crop production under deficit irrigation with poorer quality water is increasing. Drip irrigation is thought to be the most efficient irrigation method . With fertigation , the application of fertilizer can be controlled to match the plant needs at each physiological growth stage, which can enhance plant growth and increase fertilizer and water use efficiency while minimizing environmental pollution. Plant responses to salinity change with plant age, plant development, and growth stages . It is important to study plant growth response to N and soil salinity during the whole plant life cycle to reveal whether the amount of N applied alleviates or aggravates the detrimental effects of salinity during a specific growth stages . In addition, examining plant growth during the whole growing season provides information about crop salt tolerance over time. The objective of this work was to determine the influence of different soil salinity levels and N fertilization rates on the cotton growth, including the root development, plant height, and above-ground mass. The uptake of N, K, Ca, Na and Cl were measured to understand the combined effects of N and salinity on cotton growth.The experiments were conducted in a greenhouse from May to November at an agricultural experimental station at Shihezi University, Xinjiang, China . Cotton was grown in plastic pots with a volume of 84 L.
The minimum and maximum air temperature was 17°C and 32°C, respectively. The relative humidity ranged from 40– 62%. A clay loam soil taken from the station field was passed through a 2-mm sieve and packed in the plastic pots with 0.1 m increments to 0.5 m. Each pot was filled with 96 kg air dry soil. The bulk density of the packed soil was 1.2 g cm−3 and the gravimetric water content of the saturated paste of the soil was 45.6%. Selected physical and chemical properties of the soil are presented in Table 1. The experimental design was a 4×4 factorial with four salinity treatments and four levels of nitrogen. Soil salinity was created with applying NaCl and CaCl2 to the soil before the experiment. The resulting ion compositions in the treated soil were similar to those observed in the local saline soils. The soil salinity levels were 2.4, 7.7, 12.5, and 17.1 dS m−1 , referred to as non-saline , low , medium , and high saline, respectively. The low and high salt treatments were set based on the 100% and 50% yield threshold values for cotton, respectively . The amount of N was estimated with a population density of 221,000 plants ha−1 according to common field practices used by local farmers. The N application rates were 0, 135, 270, and 405 kg ha−1 , which correspond to 0, 2.65, 5.30, and 7.95 g N per pot in terms of plant population density, referred to as no , low , medium , and high fertilization. The medium fertilization level was set based on the common field practices used by local farmers. The experiments followed a completely randomized block design with four replications for each treatment. Each block included 16 treatments. Water was applied through drip irrigation units with a discharge rate of 1.1 L h−1 . Drip laterals were installed on the top of the pots, and the emitter was fixed in the centre. Each pot was irrigated by one emitter. Cotton seeds were planted at 5 cm distance from the emitter in each pot on 28 May, and then the top of the pot was covered with a polyethylene film to reduce evaporation. Each pot received 9 L of water to help germination and seedling establishment. At the three-true-leaves stage , the crop was thinned to four plants per pot, yielding a population of 221,000 plants ha−1.Fresh water was used for all treatments. Two pots for each treatment were weighed every 2 days to keep the soil water content between 50% and 80% of the field capacity during the growing season. For each pot, the amount of water to be applied was determined by gathering water discharged from the emitter close to the pot. There was no drainage or leaching through the pots. Triple super phosphate and potassium sulfate were applied as base fertilizers when filling the pots, while nitrogen fertilizer was applied through the drip irrigation system during the cotton growth period. Urea was used as the N source and applied in five equal splits at 50, 65, 78, 90 and 108 DAP, according to common field practices used by local farmers. The fertilizer solution was stored in a plastic container of 100 L volume and pumped into the irrigation system. The experiment was terminated at the boll-opening stage .Plant height was measured weekly during the growth season. The shed were collected daily for each pot. At the end of the experiment, plants were cut at the soil surface and separated into leaf, stem, bur, and seed. Roots were collected after the soil was passed through a 0.5-mm sieve with the aid of a water jet. Debris, weeds and dead roots were sorted by hand from the ‘live’ roots during washing, based on visual observation that the ‘live’ roots appeared light in colors . Each plant component was washed with distilled water, dried in an oven at 70°C for 72 h, and weighed. Dry masses of each component were measured and samples were grounded to pass through a 1-mm sieve. Soil samples were taken with a 0.03 m diameter tube sampler from three randomly chosen replicates of each treatment, at distances of 0−0.05, 0.05−0.1, 0.1−0.15 and more than 0.15 m from the emitter. The soil cores were divided into 0.1 m increments to a depth of 0.5 m, soil cores from the same treatment and depth were pooled, air dried, and a sub-sample was fine-ground with a mortar and pestle. The gravimetric water content of the soil was measured via drying in an oven at 105°C for 48 h.