SBIR-STTR Award

For over 150 years, windmills have captured wind energy to provide water for stock and human needs in remote locations. However, to manage the unpredictable energy source and ensure daily water supply, a large stock tank is required which leads to increased evaporation. Continuous winds can cause tank overflow and additional wastage. With increasing concern for diminishing water resources, this is no longer acceptable. This study will determine the feasibility of developing a wind-powered water pumping system that incorporates Compressed Air Energy Storage (CAES). The proposed system will use a wind turbine to directly drive an air compressor supplying an air storage tank at the well site. The compressor and air tank will be connected using low-cost air line, allowing the compressor tower to be placed at the optimum wind location, such as a nearby hill. A proprietary method will be investigated to maximize the energy storage in a small footprint, while also allowing compressor heat to be used to help prevent the stock water from freezing in cold conditions. The stored air will power a compressed air submersible water pump (already commercially available). CAES will provide energy storage to allow water pumping on-demand during times of no wind. Unlike batteries, CAES is tolerant of freezing conditions, will not require regular maintenance or replacement, and does not employ toxic materials. Additional advantages will also be investigated. For example, excess air could aerate the water tank to reduce bio-fouling, stagnation and mosquito larvae. OBJECTIVES: This research will determine the technical feasibility and estimate the commercial viability of incorporating Compressed Air Energy Storage into a wind-powered water pumping system targeted towards remote rural applications. APPROACH: To determine feasibility in Phase I, an end-to-end mathematical thermodynamic model of the proposed Compressed Air Water Pumping (CAWP) system will be created. This will be used to establish prototype design characteristics such as optimal working and storage pressures, compressor stage design, air tank requirements, water pump performance, and turbine rotor size for a representative range of wind resources, well depths, and water usage requirements. To be commercially viable, CAWP must be at least cost-competitive with alternative pumping methods while offering additional benefits. The proposed solution is a novel combination of many components that are already used, or similar to those used, in other industrial applications, but the correct selection, sizing and specification of each component will be critical to reducing overall cost while providing the necessary performance and reliability. For example, an arbitrarily large wind turbine, air compressor and air-powered water pump would certainly capture sufficient wind energy and lift the required quantity of water by the required height at the required rate. Likewise, an arbitrarily large air storage tank would certainly provide the required number of days of energy storage. Therefore, a key task in Phase I is to optimize factors such as pump size, operating pressure, storage pressure, storage tank size, pressure conversion efficiencies, wind turbine size, compressor design and performance, etc., to meet the required performance objectives while also minimizing component cost. In particular, the air storage pressure vessel is crucial to the design, and the best tradeoff between construction materials (steel, aluminum or composite), storage pressure (expected to be from 1,000 to 5,000 PSI), size and weight (for convenient delivery and relocation), and cost will be determined, with due consideration given to user and animal safety. With all key components specified, production and market costs will be estimated. This will allow comparisons to be made with competing methods of remote water pumping to determine if prototype development and testing is warranted in Phase II

Z4 Energy System, LLC's Compressed Air Water Pumping (CAWP) system is a new water pumping product that uses compressed air produced by wind power to operate a water pump, and stores compressed air for pumping during times with no wind. CAWP will be employed in areas where municipal water systems and grid provided electricity to operate water pumps are not available or practical. CAWP will provide a solution for water problems experienced by livestock growers that raise animals in remote pastures, organic/natural livestock producers, off-grid homeowners and recreational landowners, off-grid commercial and government facilities and municipal waste pond operators, wildlife habitat conservators, humanitarian and water relief organizations, and international users with similar requirements and site conditions. Water is a basic requirement for virtually all agricultural, industrial, urban, and recreational activities, as well as the sustained health of the natural environment. In the last 100 years the global population has tripled and the global water demand increased by a factor of six. Worldwide, a billion people do not have access to clean, sanitary water. In the U.S., the agriculture industry is the largest consumer of fresh water resources and includes 856,143 livestock operations that consume more than 1 billion gallons of water per day. During Phase II, a prototype system will be fabricated and tested under controlled, laboratory conditions to verify that operating efficiency meets computer model predictions. A prototype will then be field tested for 12 months to confirm actual performance to laboratory test results. Field trials are expected to show that CAWP features enable 21 key

Benefits:
CAES - (1) water pumping during times of no wind, (2) no batteries required, (3) energy storage method is maintenance free and (4) is not temperature dependent. On-demand water pumping - (5) no need for oversized water tank, (5) eliminates water tank overflow, (7) reduces water evaporation losses, (8) eliminates mud and ice buildup around stock tanks, (9) pond or stream water can be pumped away from riparian areas and (10) eliminates need for water holding tank for domestic use. Wind-powered air compressor powers the system - (11) excess air aerates stock tank to delay wintertime freeze-over, (12) water can be available in remote pastures longer during winter to improve pasture utilization and (13) better pasture utilization reduces cost of feed. Water pump powered by compressed air - (14) pump can pump dry without damage and (15) pumping sludge will not damage the pump. Low cost air hose transfers energy for pumping and energy storage - (16) air compressor tower can be sited in the best wind resource area and (17) air compressor tower can be centrally sited with low-cost air hose used to run multiple wells. 100% wind powered - (18) no recurring fuel costs, (19) sustainable energy, (20) benign impact on the environment and (21) eligible for renewable energy rebates, tax incentives and cost sharing programs. OBJECTIVES: Z4 Energy Systems LLC (Z4) will design, fabricate and test a prototype wind-powered water pumping system incorporating compressed air energy storage which will include a wind-powered air compressor, compact high-pressure air storage, and a float-regulated air-powered submersible water pump, based on Phase I feasibility study results. Extensive laboratory testing and one year field trials will be conducted to verify performance projections. Design goals to be met include: (1) wind-powered air compressor with drive train efficiency of at least 90%, (2) end-to-end Compressed Air Water Pumping (CAWP) system bench prototype with a thermodynamic efficiency of at least 10% and an average flow rate of at least 3.5 gallons per minute for a simulated static water level of 200', and (3) Compressed Air Energy Storage (CAES) system able to pump and maintain a 24-hour supply of water (at least 1000 gallons of pumped water). Bench testing under controlled laboratory conditions will confirm operating goals are met, prior to field testing. A field-deployable prototype will be fabricated and installed, and operate for a 12 month field trial. The prototype will be extensively instrumented to monitor and document atmospheric conditions as well as water pumping performance. APPROACH: Phase II will commence with software modeling of the wind-powered air compressor. Optimizing the prototype design via software modeling will eliminate the time and expense required to physically test multiple variations of the air compressor under varied wind conditions. The design that results from modeling will then be fabricated, incorporating off-the-shelf and custom-built components. A series of laboratory tests will be performed on an end-to-end bench prototype of CAWP. Each stage of the system will be fully instrumented during lab testing to monitor compressed air properties and determine system performance. Modifications from lab testing results will be incorporated before assembling the bench prototype components into a field prototype. Custom components will be fabricated for the field prototype including: (1) nacelle equipped with cooling vents to house the wind-powered air compressor, (2) connection plate between the air compressor and tower including a rotary air union, and (3) support rack/safety enclosure for the compressed air energy storage system. Off-the-shelf components that will be assembled into the prototype include air compressor and pressure booster, water pump, pressure vessels, air tubing and connectors. At least 12 months of field testing of the CAWP prototype will be performed. Field testing will verify performance predictions from Phase I analyses and Phase II laboratory testing. By performing the field test over an entire year, performance will be determined over a wide range a conditions and CAWP technical advantages will be quantified. A successful field test will prove the efficacy of CAWP to be a reliable water pumping system at remote sites and promote Phase III commercialization. Meteorological conditions and system performance will be monitored during field testing. Instrumentation includes: anemometer, wind vane, sensors to measure air temperature, relative humidity and barometric pressure; air flow, pressure and temperature sensors; water flow, pressure and temperature sensors; shaft encoder, vibration sensors, data acquisition electronics and time-lapse camera. Performance goals to meet are: water flow rates average at least 3.5 gallons per minute for a static ground water level of 200' and a fully-charged CAES system provides 24-hour water storage (at least 1000 gallons of pumped water) when the wind-powered air compressor is not producing (due to a no-wind condition)