Mongia explains the two most common options:
String and central-inverter-based architecture. This represents the most common power conversion system for grid-connected applications, and generally comprises three main functional blocks: The junction box in each solar panel provides the key bypass functionality. The string combiner box provides the protection and monitors the solar panel strings. The inverter provides the MPPT to adapt the impedance that the panel views at its output to obtain maximum power transfer, the DC-DC power conversion stage to adapt voltage levels, and the DC-AC power conversion stage to correctly shape the current and voltage waveforms, and to connect to the AC grid.
Micro-inverter-based architecture. This represents a fully distributed photovoltaic grid-connected system in which all the electronics is moved close to each panel. This has two main functional blocks: the micro-inverter provides the MPPT, the complete power conversion, the connectivity and AC grid connection, while the data concentrator collects the data (voltage, current, etc) coming from all the micro-inverters and sends it to a local or remote monitoring and control access point.
The micro-inverter approach is highly preferable as it results in more energy production, smart communications and monitoring, and more flexibility and reliability.
Rising use of solar water heaters
In a day a family of four uses 5.12 units of electricity to heat a hundred litres of water, leading to an emission of 4.5 kg of carbon dioxide (CO2). Installing a solar water heater (SWH) would result in a saving of 1500 units of electricity and a reduction of 1.5 tonnes of CO2 emission annually, which is close to the burning of 650 litres of petrol.
“Awareness about the positive impact of SWH on financial and environmental aspects is enabling its foray into a wider range of application segments like individual houses, residential complexes (community SWH), hospitality, education institutes, HORECA and industries. In the new residential buildings, the government has mandated the use of SWH, which has helped improve awareness as well as usage in the residential condominium segment. Attractive payback period and future savings are making this technology popular,” says Nitin Sangle, head-sales and service, solar, Racold Thermo.
There are lots of notable innovations in the SWH segment too. Here are some from Racold:
Omega flat-plate collectors. Equipped with a host of features, these collectors score over conventional solar flat-plate collectors. They have a specially-designed contact area that allows superior heat absorption, so you make the most of the sunlight! In a conventional collector, the fins and risers are bound using ultrasonic or laser welding where the area of contact/heat transfer is 106 degrees. In the case of omega collectors, the area of contact between the fins and riser is 318 degrees, drastically increasing the contact area and hence maximising the heat transfer leading to higher efficiency.
High-energy absorption tube. Racold uses 1800mm long vacuum tubes, in keeping with international standards, ensuring optimal energy absorption and higher efficiency.
Sun Max reflector. Sun Max uses individualised V-shaped reflectors that ensure 85 per cent reflectivity of sun rays onto the tube, maximising product efficiency.
Synchrophasors help improve power system visibility and reliability
Power system disturbances may occur due to various system events, transmission congestions and fluctuations in renewable energy sources. A better understanding of these disturbances is essential to detect and prevent these events before they result in failures. Phasor measurement systems are used for this purpose.
Phasor measurement units (PMUs) are time-synchronised, high-speed, measurement units that monitor the current and voltage waveforms (sinusoids) in the grid, convert them into a phasor representation through high-end computation, and securely transmit the same to a centralised server. When a phasor measurement is time-stamped against GPS universal time, it is called a synchrophasor. This allows measurements taken by PMUs in different locations or by different owners to be synchronised and time-aligned, then combined to provide a precise, comprehensive view of an entire region or interconnection.
“PMUs sample at speeds of 25 to 50 observations per second, compared to conventional monitoring technologies (such as SCADA) that measure once every two to four seconds and sometimes even once every five minutes,” adds Mohanram.
A phasor measurement system typically includes high-end computation, parallel processing and modular, expandable input/output channels. It is rugged, field-worthy, upgradeable and capable of non-stop, real-time operation. It enables utilities to proactively plan energy delivery and prevent failures.
“A synchrophasor system is a wide deployment of PMUs and dedicated high-speed communication to collect and deliver synchronised high-speed grid condition data along with analytics and other advanced online dynamic security assessment and control applications. This will improve real-time situational awareness and decision support tools to enhance system reliability. Synchrophasor measurements can also be used to improve component and system models for both online and off-line network analysis to assess system security and adequacy to withstand expected contingencies. But to realise this great potential, each interconnection must deploy a highly reliable, secure and robust synchrophasor data measurement and collection system and develop a suite of validated, highly-available, robust and trustworthy analytical applications,” explains Mohanram. The NI PMU is designed to meet the requirements of accuracy, reliability and interoperability; extreme environmental conditions, making it suitable for substation or pole mount; and advanced algorithms for event and system analysis.
Performance optimisation at source
It is interesting to note that the role of technology begins at the very beginning of the value chain. Performance optimisation measures taken at the fuel exploration and energy production sites also play a major role in improving the energy availability and costs.
“Increasingly, oil and gas companies are investing in technologies to realise the potential of the ‘digital oilfield.’ Advanced analytics, Big Data, complex event processing and high-performance computing are being used to enable organisations to optimise performance in oil drilling and production. Technology companies like ours are investing in solutions designed for exploration and production companies in the energy sector that reduce exploration risk, cost per barrel and improve performance of oilfield assets,” says Sanjay Kalra, vice president and head of delivery-Energy and Utilities, iGATE, the integrated Technology and Operations (iTOPS) company providing business outcome-based solutions.
Tools for developing innovative solutions
As with any emerging field, the energy sector also needs efficient tools to design, develop, test and deploy new technologies.
“The key to building an innovative solution is the ability to quickly prototype and prove its utility, adhering to the standards and protocols that are followed in the energy sector, and meeting the reliability/durability requirements,” says Mohanram.
“This brings us to the discussion about tools that can help developers build these systems. There is a significant leverage of cutting-edge PC technologies in today’s energy management systems. This trend has channelled people towards commercial off-the-shelf (COTS) hardware platforms and high-level software tools that provide enough abstraction for a domain expert to put together the system. The COTS hardware platform takes care of adhering to the mechanical and electrical standards and the high-level software provides readymade libraries for the protocols followed in the Industry.”
Reconfigurable embedded instrumentation and control systems, such as National Instruments’ CompactRIO, provide an ideal combination of technologies and features to address the most difficult smart grid challenges. Powered by NI LabVIEW and reconfigurable field-programmable gate arrays (FPGAs), these user-programmable, field-updatable smart devices can perform multiple digital signal processing and control tasks in parallel and in real-time. Furthermore, modern analogue-to-digital converters (ADCs) and sensors provide high-fidelity electrical measurements while synchronising on a global scale. In addition, emerging network communication protocols such as IEC 61850 are being defined to ensure network interoperability and compatibility from the smart sensor to the cloud.
Double-click on energy
Slowly, we can see that technology is changing things in the energy sector. Dr Kumar points out that today’s companies are taking an active interest in making their operations more efficient and effective. Individuals are becoming more and more aware of their power usage and ways to conserve it. So far, energy production had been centralised to adapt to the demand variation. Renewable energy generation is enabling an era of distributed generation that can integrate with the grid, which can help in reducing transmission and distribution losses as well as cater to peak demand. Attempts are being made to make the transmission and distribution systems more intelligent and flexible. HV/MV and MV/LV substations with indoor solutions for limited space, urban and outdoor areas, as well as unmanned solutions for rural and remote landscapes guaranteeing safety of people and assets, are an illustration of this. Substation automation and renewable energy connectivity are other examples.
“However, we feel India still has a long way to go when we talk about smart monitoring solutions. Technology is available here, but a wide acceptance from common people is lacking. The concept of energy monitoring and management is growing fast in the country but a large chunk of buildings and industry still lack these latest technologies,” says Dr Kumar.
It is obvious that all the required technology is here. What we need is a change in mind-set. As Prof. Bhave innovatively terms it, we need to double-click on energy!
“Ambient energy—sunlight—is everywhere and plentiful, yet when we speak about energy we typically mean fuels—coal, oil, gas, wood, or nuclear—and often their use for generating electricity or for transport. Instead, we could be talking about use—cooling or refrigeration, heating water and air, and mobility (public and personal transport)—and less about litres and kilowatt-hours. Can we parse the electricity bill into water heating, cooking, air-conditioning and transport? Why do we measure kilowatt-hours in undifferentiated bulk each month? The point is, energy—as we use the term—is amorphous and not enlightening; we need to double-click on it,” says Prof. Bhave.
“We use a lot of appliances today—refrigerators, microwaves, washing machines, lighting, air-conditioners. We don’t have month-to-date energy use and its cost. We don’t know easily how much each hot-water shower costs. Or the hourly cost of refrigeration. If we can have per second mobile phone billing, surely this can be done for electricity? It is interesting to speculate why this is not the case. The technical solution is not difficult. IT has a big role to play. I think this area is ripe for technical and business model innovation. The risk is timing,” he adds. Food for your thought!
The author is a technically-qualified freelance writer, editor and hands-on mom based in Chennai
