Renewable energy

Biofuel is produced from biomass resources to make liquid fuels like ethanol, methanol, and biodiesel, and gaseous fuels such as hydrogen and methane (see Biogas). Biofuels are primarily used to fuel transportation vehicles, but they can also fuel engines or fuel cells for electricity generation. Biofuel level applications FERMENTATION: In ethanol production, fermentation provides a series of chemical reactions that convert sugars to ethanol. Ethanol and carbon dioxide are produced as the sugar is consumed by yeast or bacteria. Level control of the fermentation tank must tolerate agitation, aeration, and the presence of froth or foam. REACTOR TANK: Biodiesel and cellulosic ethanol production use reactors for chemical addition and mixing. In a Continuous Stirred-Tank Reactor one or more fluid reagents are introduced into a tank reactor equipped with an impeller that stirs the reagents to ensure proper mixing. The reactor tank requires level monitoring and alarms. REAGENT TANK: A reagent is a compound that is added to a system in order to bring about a chemical reaction. In biodiesel production, an alkali reagent is used in titration, a test used to determine how much catalyst is needed to achieve a reaction. Reagents are stored in tanks equipped with level controls. SUMPS: Liquids are collected in sumps and pits during hydrolyzation, fermentation, distillation and glucose processing of biofuels. As the liquid level rises or falls in a sump, a level switch can actuate or deactuate a pump or activate an overfill alarm. LIQUID STORAGE: A wide array of liquids are stored at biofuel plants including water, biodiesel, methanol, ethylene, catalysts, and waste liquids. Level instruments monitor inventory levels and protect against overfills and underfills that cavitate pumps.

Biogas from digesters is typically 60–70% methane and 30–40% carbon dioxide. Biogases fuel engine-generators or gas turbines to produce electricity. They also fuel boilers to produce heat or steam. Biogas utilization has increased in industrial processing, wastewater treatment plants, municipal landfills, and livestock farms. Biogas level and flow applications BIOGAS FLOW: In all forms of biogas production, safe and reliable gas flow measurement is essential in the collection, disposal or re-use of biogas. Thermal mass flow meters are widely used in landfill, anaerobic digestion and gasification processes. A flow meter measuring biogas must provide low flow sensitivity, low pressure drop, and tolerate temperature and pressure changes. SCRUBBER VESSEL: Essential in gasification processes, scrubbers remove odors, pollutants, acid gases and chemical wastes from biogas. Accurate level monitoring of the scrubbing water necessitates a control to automatically feed the correct amount of make-up water to the recycle reservoir either continuously or on a periodic basis. The level monitoring device for water-out control should be equipped with a level alarm. BIOGAS DEHYDRATION: As biogas emerges from a digester or a landfill it is saturated with water that causes corrosion problems upon condensation. Dehydration systems using air, vacuum and desiccant processes to remove water typically include a holding tank for water drawn off the gas with a level control actuating a valve to vacate the tank at high level. Biogas is dehydrated according to the customer’s specifications for maximum water content. Some uses, such as boiler fuel, require an extremely dry gas.

Geothermal reservoirs located deep underground provide powerful sources of heat energy. Drilling a geothermal well to a reservoir brings hot water and steam to the surface where it can be put to many uses. Geothermal level applications STEAM/BRINE SEPARATOR: To achieve better conditions for turbine operation, a reservoir’s steam and brine (salt water) is separated into streams where the brine water and particulate matter settle out and the steam vapors rise. The steam collects at the top of the separator where it is removed. Liquid level control modulates the amount of water that is drawn off. DEGASSER TANK: Geothermal hot water is often routed through a degasser—a large insulated tank equipped to remove organic gases and provide displacement with air or nitrogen. Degassing operations provide treatment by way of carbon adsorption, thermal/catalytic oxidization, combustion, vacuum induction, or by a series of condensers. WATER STORAGE TANK: Water tanks include those for heated water, cooling water, and wastewater. Direct heat use applications require heated water storage. Spent geothermal fluids with high concentrations of chemicals are stored prior to treatment and reinjection into the reservoir. Hot water can be cooled in special storage tanks to avoid modifying the ecosystem of natural bodies of water prior to reinjection. FLASH TANK: Hot water from the geothermal well enters a flash tank where the reduced pressure causes the water to boil rapidly, or “flash” into vapor. Water that remains liquid in the tank is returned to the groundwater pump to be forced down into the reservoir again. The vapor from the flash tank drives the steam turbine. VAPORIZER: In these special heat exchangers, the geothermal fluid heats and vaporizes a secondary “binary” fluid, which is typically an organic liquid with a low boiling point. The organic vapor drives the turbine. The level of water in the tank must be monitored.

Hydropower is electricity produced from flowing water. Hydropower produces approximately 7% of U.S. energy (19% of world energy) and accounts for 45% of total renewable energy in the U.S. Newer technologies harness energy in ocean tides, waves, and currents. Hydroelectric level and flow applications SURGE TANK: The main function of a surge tank is to control pressure variations due to rapid changes in the velocity of water. When the power turbine is running at a steady load, there are no surges in the flow of water since the quantity of water flowing through the conduit is sufficient to meet the turbine’s requirements. When turbine load decreases, a governor closes the gates of the turbine to reduce water supply. The water is routed for storage in the surge tank—an action that prevents the conduit from bursting. When turbine load increases, additional water is drawn from the surge tank to meet the increased demand. A surge tank’s internal diameter may range from a few feet to several dozen feet. The tank relies on a level sensor to determine whether or not water stored in the tank should be removed. PUMP PROTECTION: Flow Switches protect pumps from damage due to leaks or if a valve is accidentally closed downstream. A switch will actuate an alarm and shut down the pump when flow drops below the minimum rate.

Solar Technologies use the sun’s energy to provide electricity, hot water, process heat and cooling. Solar power presently provides less than 1% of U.S. energy needs but this is expected to increase with the development of more efficient solar technologies. Solar level and flow applications HEAT TRANSFER FLUID STORAGE: Large-scale solar collectors for electric power generation require a heat transfer fluid (water, thermal oils, or ionic liquids) to absorb the sun’s heat for generating steam. Arrays of mirrored panels convert the sun’s energy into +750° F (+400° C) thermal energy that’s hot enough to create steam for turbines. The mirrors focus sunlight onto pipes of heat transfer fluid that run along the mirror’s centerline. The fluid then boils water to produce steam. Thermal fluids also help provide hot water and heat. Thermal fluids are typically stored in pressurized tanks that require level monitoring. HOT WATER STORAGE: High-temperature solar water heaters provide energy-efficient hot water and heat for large industrial facilities. Thermal storage in buffer tanks provide interfaces between collector subsystems and energy-using systems. The preferred solar storage vessel is a vertical cylindrical tank designed for the maximum pressure of the supply water source, which may be as high as 150 psi. PUMP PROTECTION: Flow Switches protect pumps from damage due to leaks or if a valve is accidentally closed downstream. A flow switch will actuate an alarm and shut down the pump when flow drops below the minimum rate.

Wind energy is one of the fastest-growing forms of electricity generation in the world. U.S. wind power market share is expected to reach 3.35% by 2013 and 8% by 2018. More optimistic industry experts predict that wind energy will meet 20% of the nation’s energy needs by 2030. Wind turbine level applications WIND TURBINE OIL RESERVOIR: As wind energy technology advances, higher demands are placed on turbine lubrication systems. Lubricant reservoirs of up to 550 gallons (2,000+ liters) serve as oil storage in centralized systems to provide lubrication for the blade bearings, blade tilt, main bearing, azimuth bearing, meshing gears, generator bearings, cylindrical gears, bevel gears, rolling and sliding bearings, worm gear units, and gear couplings. The oil reservoir is monitored for continuous or point level. WIND TURBINE GEARBOX: Gearbox and bearing lubrication are of particular importance due to the complexity of the gearbox and the high mechanical loads. Gearbox and bearing problems are a common cause of downtime; and loss of oil through a small leak has lead to catastrophic wind turbine failures. Along with vibration, temperature, and flow sensors, a low level gearbox oil alarm is a critical safety control. Water pumping level application WATER PUMPING STORAGE: For industrial and agricultural use, a water pumping windmill is typically placed above a well or near a river. Next to the mill a storage tank is placed to provide a buffer supply of water for when the mill is not operational. Ferro-cement and steel tanks are typically used. Other wind energy applications Municipal and Industrial Water Services Mechanical Power Mills Telecommunications and Radar Pipeline Control Navigational Aids Cathodic Protection Weather Stations and Seismic Monitoring