Solar power is the most plentiful source of energy on the planet. Light from the sun can be directly converted to electricity via photovoltaic (PV) cells or by using heliostats, which include mirrors or lenses, to concentrate sunlight to a central receiver that collects the solar energy and converts it to heat (concentrated solar power or CSP). According to the Solar Energy Technologies Office, the thermal energy generated can then be used as a power or heat source in many industrial applications including power generation, water desalination, chemical production, and enhanced oil recovery. Additionally, through the use of thermal storage, CSP technology can provide solar power-on-demand — addressing grid integration challenges caused by solar energy variability. Thermal solar fields and CSP installations require supplemental power to reposition arrays during high wind loads.
A parabolic trough system is a type of CSP technology that is comprised of large mirrors shaped like the letter U. These troughs track the sun during the day. The sun's heat is reflected and sent to a receiver tube that contains a heat-retaining fluid. Basically, this super hot liquid heats water in a heat exchanger and the water turns to steam. The steam is sent off to a steam turbine, and from there, a generator producing electricity. Ultimately recyclable, once the fluid transfers its heat, it's recycled and used over and over. A major benefit of a trough system is that the heated fluid can be stored and used, even on a cloudy day or after the sun has set.
From towers to dishes to linear mirrors to troughs, concentrating solar power (CSP) technologies reflect and collect solar heat to generate electricity. A single CSP plant can generate enough power for about 90,000 homes. This video from the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy explains what CSP is, how it works, and how systems like parabolic troughs produce renewable power.
Some of the solar installations have an array of solar panels (PV), or parabolic mirrors (CSP) which will move as the sun arcs through the sky. The main goal here is to place the mirror or panel at the proper angle to the sun in order to capture the most energy. This movement may be affected by a hydraulic cylinder, electrohydraulic or all-electric actuator.
Hydraulic piston accumulators can be incorporated into solar tracking systems for several reasons:
- To reduce load demand. The ability to store hydraulic fluid under pressure so that larger hydraulic pumps are not required (smaller pumps can gradually build pressure in the accumulators. If the accumulators were not present, the pumps would have to be sized to run any time array movement was needed and also be larger in size in order to accommodate any large array movements
- Accumulators may be installed in order to provide emergency shutdown power. The arrays must have the ability to be stowed in a high wind situation. In the event of an electrical system failure, the accumulators could provide reserve power to move the arrays into a safe position. When used as an auxiliary energy source, an accumulator can reduce the hydraulic system requirements, and can be used as an energy storage link so energy can be reasonably distributed.
- May provide some cushioning or dampening of the array as they are exposed to high wind loads.
For hydraulic actuators, a power source is needed, and an accumulator could be used in two applications within this hydraulic system:
- As an emergency power source: If the hydraulic power unit(s) that control these actuators fail – either through a component failure or electrical power loss, an accumulator, with its stored hydraulic energy, can be used to move the array to a “safe / stowed” position. This safe position protects the array from high wind loads which could damage it.
- For power augmentation: It may be possible to design a hydraulic power unit with less flow capacity in order to save space, cost and/or electrical power requirements. In this instance, an accumulator would allow for the gradual accumulation of hydraulic power (both pressure and flow). This power reserve can then be tapped into when needed – providing a greater flow than what the small hydraulic power unit could produce by itself. An application of this would be for emergency stowing of a number of arrays
A piston accumulator is a kind of pressure containment vessel. Its function is to absorb hydraulic shock, eliminate pulsation and reduce noise. It can also have the function of energy storage, energy recovery and energy compensation for the system.
The accumulator is comprised of a cylindrical barrel, a piston that travels along a guide rod within this barrel, and end caps with ports on either end of the cylinder – one port exposed to the hydraulic system, and the other port for an isolated, inert gas volume. Hydraulic pressure and oil volume enter into the accumulator on the system side of the piston. This pressure moves the piston within the cylinder barrel, compressing the gas that is on the opposite side of the piston. If hydraulic pressure is lost, as in the event of a hydraulic power unit failure, this highly compressed gas will expand, moving the piston and forcing the hydraulic fluid out of the accumulator into the hydraulic system. This stored energy/pressure can then be used to do work – move a cylinder or actuate a valve.
Watch this video to learn more about a piston accumulator's operation
Benefits
When used as an auxiliary device of a hydraulic system, an accumulator offers
- Economy
- Safety
- Energy savings,
- Reliability
- Environmental protection
When used as an auxiliary energy source that augments a hydraulic pump, an accumulator can reduce the pump capacity requirements and can be used as an energy storage link, allowing the stored energy to be quickly distributed. The loading mode and cycle frequency of an accumulator determine the relative longevity of an accumulator, with low cycles resulting in longer operational life. An accumulator plays an irreplaceable role in maintaining the normal operation of the hydraulic system, improving its dynamic quality, maintaining working stability, prolonging working life and reducing noise.
Safety considerations
An accumulator is one of the more dangerous parts of a hydraulic system, so special attention must be given to safety during operation. One of the first steps to safety in a hydraulic system is identifying the accumulator. It should be labeled with the part number, manufacturer, serial number, maximum pressure and pre-charge pressure -- a good rule of thumb is to always consult an expert when working with accumulators.
Designed for use in critical hydraulic applications, Parker's SBA Series Accumulator Safety Blocks make it possible to protect, isolate, and discharge hydraulic accumulators from a single device. Each incorporates a shut-off, pressure limiting, and pressure release feature in one housing rated for working pressures to 350 bar. Modular in design, Parker's SBA line uses an integrated manifold approach to reduce plumbing and leak points. All safety blocks have 2 maintenance ports and can be used with bladder, piston, and diaphragm accumulators.
The SBA Series accumulator safety blocks are designed for use in a wide variety of critical hydraulic applications to benefit end-users in several ways including:
- Compliance (for systems where shut-off, pressure limiting, pressure release and measurement point functions are required on accumulators)
- Fit (compact design makes them ideal for applications where space is limited)
- Productivity and Uptime (blocks help speed-up maintenance procedures/reduce system downtime)
Parker SBA Safety Blocks represent a single-unit solution for manufacturers tasked with European Pressure Equipment Directive (PED) 97/23/EC compliance. The directive states a safety device must be fitted to all accumulators to provide a shut-off facility, pressure limiting and pressure release function as well as measurement points. A CE-certified relief valve is also included on all units to satisfy PED compliance. New SBA Safety Blocks are suitable for use with all types of accumulators - bladder, piston and diaphragm. Their compact, multi-function design saves space and reduces connections.
"In comparison with traditional safety systems, the new SBA Series makes it possible to protect, isolate and discharge a hydraulic accumulator from a single unit. Each SBA Safety Block incorporates a shut-off, pressure limiting and pressure release feature in a compact and robust housing rated for working pressures up to 350 bar. As leaks are also a safety concern in any hydraulic system, the integrated manifold approach of our product provides added value through the elimination of plumbing and leak points."
Bryan McGehee, application engineer, Parker Hannifin Corporation, Global Accumulator Division
Choosing an accumulator
To ensure safe operation, when choosing an accumulator for a CSP application, it is important to consider the technical requirements and capabilities of the product, as well as the reputation of the supplier and support services they provide. Some key things to look for include:
- Dependable performance for extended periods in harsh environments
- Long service life
- Low leakage
- Regulatory certifications such as ASME, DNV, ABS, AS1210, SELO, CRN, NR-13, PED(CE), DOSH
- Corrosion performance up to 720 hours
Questions to ask a supplier include:
- What type of after-sales service and support does the organization provide?
- Is the product supported by professional engineers with expert product knowledge in accumulator technology and regulation?
- Does the supplier offer preventive maintenance programs?
- What are the lead times?
Parker piston accumulators, for example, are an optimal choice when fluid energy storage, hydraulic shock adsorption, auxiliary power or supplemental pump flow is required. As the world’s leading manufacturer of hydraulic piston type accumulators, Parker has the ability to combine high volume production along with completely custom designs due to our extensive manufacturing capabilities. This allows us to manufacture the standard line of piston accumulators as well as create highly unique and custom piston accumulators for a wide variety of applications at competitive prices.
Features and benefitsHeavy-duty service with high operating pressures up to 20,000 PSI
- Lower gas permeation rate
- Extremely high-flow rates
- Unlimited compression ratio
- Can be used with remote gas bottles
- Gradual failure mode
- Sensors can be fitted for performance monitoring
- ASME, DNV, ABS, AS1210, SELO, CRN, NR-13, PED(CE), DOSH certified
- Five standard seal options to handle a variety of fluids and temperatures
- Technical and aftermarket support
- Local design and engineering capability and support
- Competitive price
- 4-8 weeks delivery
Noor Energy 1 uses Parker piston accumulators
A recent solar project highlights a few challenges faced by the use of CSP.
The Noor Energy 1, the 950MW CSP+PV solar power project in Dubai, now in Phase 4, has broken a dozen world records in solar CSP history. It has three technologies to produce 950MW of clean energy — 600MW from three parabolic trough CSP plants, 100MW from a solar tower, and 250MW will be generated from photovoltaic panels.
The initial 700MW CSP project will be completed by the end of 2022. The first parabolic trough CSP plant is planned to be operational on August 21, 2021, the central tower CSP plant finished on November 21, 2021, and the second and third parabolic trough plants to be completed by the end of 2022.
8 of the world records for CSP industry made by Noor Energy 1
- World largest single-site investment project in CSP based on IPP model—USD 4.4 billion (AED 15.78 billion)
- World largest capacity of single CSP+PV project—950MW
- World largest area of single CSP+PV project—44 square kilometers
- World biggest quantity of molten salt used in single CSP project—550,000 tons
- World tallest CSP tower—260m
- World-leading tower wireless heliostat technology—70,000 heliostats
- World largest trough in commercial CSP project—8.2m
- Most competitive LCOE—USD 7.3 cents /kWh
Article contributed by Spencer Sun, territory sales manager, Industrial Hydraulic - North China, Parker Hannifin with support from the Global Energy Team.
Additional articles on Solar applications in Power Generation:
Solution for Capturing Maximum Solar Energy Includes Helical Actuator
How Renewable Energy Power Plants Can Increase Output and Decrease Costs
Improve Solar Panel Maintenance and Condition Monitoring Efficiency
IoT Solutions Reduce Time and Cost for Solar Panel Inspection
Parker Solutions for Power Generation
Large Capacity Piston Accumulators Help Subsea Engineers Meet Extreme Demands
Though gas-powered, internal combustion engine driven vehicles have been the norm in the automotive industry for over 100 years, electrification is growing. The traditional engine design was efficient, reliable, and easy to use, but gasoline powered vehicles are loud, dirty, and harmful to the environment. Given these drawbacks, electric vehicles have started to gain market share in commercial and personal markets. Public transportation is moving toward electrification at a faster pace than other markets, spurred by the deployment of electric vehicles in China.
The eHPS is ideal for buses and large commercial vehicles that require large amounts of hydraulic power for steering assistance, but also necessitate the quiet operation of an electric system. In addition, the eHPS has IP67 protection, is tested to SAE J1455 vehicle standards, and designed to ISO 16750 standards, making it ideal for replacement applications. Electrification is the future of the automotive industry, and public transit is leading the charge. 
This article was contributed by CT Lefler, marketing product manager (e-business), Pump & Motor Division, Parker Hannifin Corporation.
Phil Meyer, operations manager of the Whitman County Public Works Department, in Washington State, is tireless in his search for the right tools to help his 42-person team maintain over 1,900 miles of roads and 360 bridges and large structures in Southeastern Washington. The department has a daunting workload and inclement weather that can border on the extreme, productivity, durability and versatility are critical requirements of the equipment used at Whitman County. Typical projects include ditching to maintain flow lines, culvert maintenance, placing rip-rap, brush removal, bridge demolition, gabion basket installation, sloping and more.
The seven PowerTilts and their PowerGrip have been important assets for the Whitman County Public Works department. With PowerTilt and PowerGrip, the department accomplishes most tasks 25 to 50 percent faster. The Whitman County Public Works department has even recommended PowerTilt and PowerGrip to other local agencies such as the Washington State Department of Transportation and the North Latah County Highway Department in Idaho.
PowerTilt uses Parker’s innovative sliding-spline operating technology to convert linear piston motion into powerful shaft rotation. Each actuator is composed of a housing and two moving parts — the central shaft and piston. As hydraulic pressure is applied, the piston is displaced axially, while the helical gearing on the piston outer diameter and housing’s ring gear cause the simultaneous rotation of the piston. PowerTilt's end caps, seals and bearings all work in tandem to keep debris and other contaminants out of the inner workings of the actuator.
Over a decade of research, innovation and engineering has gone into making the PowerTilt and PowerGrip attachments integral solutions for work site efficiency. PowerTilt’s robust design has allowed Whitman County Public Works to keep a PowerTilt on their machine 100 percent of the time, year-round. 
This article was contributed by Jessica Howisey, marketing communications manager and Daniel Morgado, applications engineer, Helac Business Unit, Cylinder Division.
Gold Cup Heavy-Duty Pumps and Motors have long been respected in the industry for technical excellence in hydrostatic transmission applications in marine, drilling and shredding applications, among others.
