In Masdar City—a celebrated, centrally planned community in Abu Dhabi, UAE—temperatures recently reached a record of more than 51 C. The city is being built by the Abu Dhabi Future Energy Company with additional funding from the Abu Dhabi government. A long-term, truly sustainable view of capital investment is clear. At the moment, 100 percent of the electrical demand is provided by photovoltaic power generation. As the city population grows and demand for energy increases, it is expected that the existing 10-megawatt (MW) solar installation will provide 20 percent of the city’s electricity, with the remaining 80 percent coming from alternate sustainable sources.
City planners began the project by focusing on minimizing the total energy requirements through passive means, carefully managing the orientation and form of buildings for maximum efficiency (see Image 1). As a secondary step, planners looked for advanced solutions in building performance optimization and other active controls.
Image 1. Masdar City’s layout
The city has implemented stringent building efficiency guidelines for insulation, lighting, window glazing, reliance on natural light and the installation of smart appliances. To help manage the electrical network and minimize electrical demand through informed decision-making, the city requires the installation of smart meters and building management systems. It also relies on an integrated distribution management system to monitor and manage energy usage patterns.
Masdar’s perimeter wall is designed to block hot desert winds, and the minimal use of motor vehicles allows for narrow shaded streets that help funnel cooler breezes across the city. An updated version of the cooling tower concept has been included and also contributes to this effect.
Buildings in Masdar must also have energy-efficient cooling systems, given that the city’s raison d’être is to serve as a model of environmental responsibility. The original goal was to rely entirely on renewable energy with a sustainable, zero-carbon, zero-waste ecology and to become a world-leading hub for companies in the clean technology sector. Masdar City is already home to the headquarters of the International Renewable Energy Agency (IRENA), several international ecology conferences, one of the world’s largest solar farms and the Masdar Institute of Science & Technology. The community puts a strong emphasis on technology-driven energy efficiency, and this priority is reflected in the design of its pumping systems.
The contemporary pump technology, design principles and installation approaches used in Masdar contribute to improved energy performance, easier maintenance a more stable operation than is offered by conventional set-point-feedback control systems.
If someone needs a big truck for 15 days each year and a small car for the other 350 days of the year, it is not an optimal solution to buy a big truck. So the pump company responsible for the Masdar system employed only intelligent, pre-packaged fluid management equipment and worked with engineers to initiate design planning for the use of demand-based control in Masdar. Demand-based control is a system optimization method for HVAC systems.
Sensorless Demand-Based Control
A pump company’s design-envelope technology plant’s packages and controls use the Equal Marginal Performance Principle (EMPP) established several years ago as a way to realize efficiency improvements of 25 to 50 percent more than equivalent conventional set-point methods for operating HVAC systems.1
The EMPP states that the energy performance of any system that operates with multiple modulating components is optimized when the marginal system output, per unit energy input, is the same for all individual components in the system.
The embedded control technology manages equipment according to optimized, system-wide power relationships, rather than meeting intermediate temperature or pressure set-points. Design envelope technology also offers sensorless demand-based control, which reduces the costs for equipment purchase, installation and commissioning.
On the more than 30 pumps in the university buildings at Masdar City, no external sensors are installed. The cooling systems rely on prefabricated, integrated pump stations called design envelope intelligent fluid management systems (IFMS). IFMS stations consist of a number of precisely matched, vertical in-line pumps with integrated controls, plus an intelligent pump control unit. The control unit calculates the head and flow requirements in real time, enabling pump speed adjustments based on the immediate demand for cooling.
Design envelope technology provides very high efficiency levels across a wide design/performance range, regardless of the operating point. This ensures that pumping systems consume as little energy as possible. It also allows installations to exceed American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90.1 guidelines for 2010, mandating 70 percent energy savings at 50 percent of peak load, with resulting carbon emissions well below the current legal requirements.2 It lets owners buy a small car rather than a big truck, while enjoying both the performance of the truck and the energy and cost advantages of the small car.