Environmental issues are never long making headlines across the world. The latest pronouncements from the Intergovernmental Panel on Climate Change emphasises the need for more and tougher limitations on carbon emissions.
While China’s expanding economy is cited as a prime culprit, the country is simultaneously a source for many major scale renewable energy projects – undertakings that have provided new opportunities for the UK pumps market.
SPP Pumps is a case in point: the company’s Pump as Turbine (PaT) solutions have been in demand there, notably for the Sha Tin Water Treatment Works in Hong Kong. The site has developed a hydro recovery system with SPP, aimed at generating its own power on site.
Harnessing potential energy from water as it enters the WtW, it generates electricity that contributes to the power needs of the site.
Pumps as turbines or ‘pumps in reverse’ have been a familiar concept for nearly a century, when it was ascertained that reversing the flow could have the net effect of allowing the machine to function as an effective turbine. With the rotor operating in reverse and with the pump linked to a motor, the latter is able to generate electrical power.
The sector itself could make a major contribution to the access of both energy and water in a sustainable way, in many regions of the world, if more investments were made
Gary Wilde, technical services officer, British Pump Manufacturers Association
The ability to switch direction transformed the limited nature of hydro-electric generation; electricity was employed to pump water from a lower to a high reservoir and store energy – “a free fuel source which is potentially everlasting,” as SPP puts it.
Since the growth of hydro-electric in the 1930s, the game changer has been, as in other industries, the development of the variable speed drive.
The potential savings in efficient energy use can be illustrated with GE’s example of hydro-electric storage with an upper and lower water reservoir: If a plant operates three 100MW pumps with fixed speed pumps and receives 270MW of electricity off peak, only two pumps can start and the upper reservoir is charged by 200MW with 70MW going to waste.
Variable speed pumps allow all three units to adapt their speed to ensure exactly 270MW is stored, ensuring a lack of waste.
Growth of interest in renewable energy sources has both encouraged and been aided by VSD technology. Not least because sources such as solar and wind are themselves variable and require system flexibility in order that they provide stable input to the energy grid.
Gary Wilde, technical services officer at the British Pump Manufacturers Association, has no doubt that the potential is there for pumps manufacturers to realise the benefits from growing interest in renewable energy sources: “There are a few pump manufacturers investing in renewable energy technologies in the pump industry but the sector itself could make a major contribution to the access of both energy and water in a sustainable way, in many regions of the world, if more investments were made.”
In areas with no access to grid connections, photovoltaic (PV) and wind energy pumps have a huge potential to supply essentials such as water, says Wilde.
“According to reports the pumped hydro storage market is to surpass US$350 billion worldwide by 2024 but requires the right terrain in which to operate.
“There is an increasing need for a stable and pollution-free environment which should encourage regional governments to implement more advanced power generation projects where possible.”
While a recent Drax report queried whether renewables use and contribution to the electricity sector will continue to expand at its recent rate in the UK, for the pumps sector there remains another aspect of energy consumption that is not limited to the one process sector; the energy efficiency of the products themselves.
Wilde notes that minimum energy efficiency requirements imposed within the EU for clean water pumps and circulators have extended further.
“It has gone beyond the product (pump) unit itself to now looking at the extended product (pump, motor and VSD) and the system as a whole.”
But the catalyst for this extended product approach is less to do with legislative rules and more concerned with the energy savings potential that could total some 35TWh per year, he advises.
Additionally, says Wilde, the European Union is also looking at other areas such as booster sets and wastewater pumps that will further increase gains. Brexit or not, it is unlikely the UK’s regulation will not continue to align with standards in Europe.
While many pump systems are still not designed with energy as a prime consideration, Wilde emphasises that, “if pump systems are initially designed on an energy efficient basis and pumps are correctly applied and sized the energy savings will often be in excess of 50%”.
For this, five criteria must be addressed: plant design; pipe work configuration and restrictions; liquid velocity in pipe work; system characteristics and pump selection; pump and system controls.
Once installed, the challenge is to maintain machines in prime working order to avoid the interruptions caused by downtime and corrective maintenance. The key indicators are well known to those in the pumps industry.
These include flow, pressure, power, speed, temperature, vibration, corrosion, lubrication and wear, plus leak detection – all of which can be addressed by efficient condition monitoring.
Says Wilde: “An effective pump condition monitoring system (CMS) will be capable of overseeing the operating conditions of the pumps, issue any advance warnings of possible faults and predict the residual lifespan of critical machine components prior to final breakdown.”
However, some aspects of energy consumption can be harder to spot, warns Tom Grove, CEO at AESSEAL Inc. A case in point is mechanical seal friction.
“Mechanical seal friction accounts for a tiny percentage of the total energy consumed on a pump and so is easy to overlook. However, to function correctly mechanical seal faces must be flushed with a cool, clean liquid to provide lubrication, prevent overheating caused by dry running, and maximise reliability.”
In many applications, says Grove, this is provided from a separate seal support system or piping plan – and it is the energy consumed indirectly by the piping plan that can be considerable.
“Identifying unnecessary energy consumption can be as simple and low cost as carrying out a periodic seal energy audit, where the mechanical seal acts as the ‘canary in the coalmine’, identifying unnecessary power consumption caused by the energy-inefficient seal support systems on a pump.”
Niche focus, big impact
Plant data collection is essential and by calculating heat flow, one can assess the energy impact of each individual mechanical seal on the plant. High-energy use can be easily identified and reviewed to identify a potentially more efficient seal support configuration.
“Environmentally-friendly ‘continuous loop’ seal support systems have been developed in recent years. These manage water sustainably by employing an integral vessel to store flushing water for continuous recycling,” says Grove.
“The barrier fluid is circulated to and from the mechanical seal by thermosiphon, a method of passive heat exchange which circulates the fluid, minimising wastage and providing more efficient cooling.”
He quotes the example of a typical paper mill that might inject six litres of water for flushing and cooling, before being evaporated off. Investment in a continuous loop water management system would lead to reduced energy usage of over 50,000mmBTU, calculates Grove.
This would achieve savings of over £400,000 and a ROI of 3-4 months, in addition to improved plant reliability and reduced maintenance times.
Globally, industry investment in energy efficiency experienced a marked fall recently. The World Energy Institute’s report revealed a rate-of-growth drop of 8% in 2017, and this was most noticeable in China where growth rates fell to 15% – a dip of 20 percentage points over the previous year.
While the gains made in niche areas are miniscule in world terms, their potential for scaling up and their application to many industrial scenarios will be key, not least for the pumps industry.