Giving Solar the Edge

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A quiet revolution from SolarEdge means their technology is disruptive because of its benefits, but complementary by its fit into the current PV workflow.

May 27, 2010
Elizabeth Engler Modic

SolarEdge aims to maximize energy harvesting while minimizing cost and safety risks.The goal is to maximize power generation for residential and large-scale systems, while reducing costs and complexities. Still, the question remains: How?

SolarEdge Technologies, founded in 2006, is working to address challenges by delivering next-generation power conversion electronics that overcome limitations of existing photovoltaic (PV) systems – having successfully married the traditional PV workflows and installation methods with their own holistic system approach.

“Traditional PV systems suffer from a broad range of limitations that prevent them from reaching their full potential,” says Lior Handelsman, VP of product strategy and co-founder of SolarEdge Technologies. “As a result, solar installations cost more and do not produce at maximum efficiency.”

Some of the limitations are:

  • Power losses;
  • Complex system design;
  • Insufficient monitoring;
  • Safety hazards; and
  • Limited scaling, retrofit, and repair options.

Current PV

In the case of current residential and commercial PV systems, they are typically built using ten to a few hundred PV modules connected in a series-parallel connection. Several modules are connected in a series, forming a string, to achieve a voltage high enough to enable efficient DC/AC inversion – usually between 150V and 600V. Additional power can be added to the system by adding multiple strings in parallel.

Since the strings are connected in parallel, each string must have the same operating voltage. Therefore, in order to efficiently produce power, each string must match others in operating voltage. This generally includes matching the module make and model, string length and orientation, and shading conditions, to name just a few parameters.
The entire array is connected to a solar inverter, which is responsible for harvesting the electrical power and inverting it to AC so it can be fed into the grid. If an array consists of two strings with different operating voltage characteristics – module model or module orientation – two inverters will be needed.

In the past, partial shading limited traditional PV systems from reaching their full potential.The series connection in each string also poses problems that reduce the maximum power available for inversion, stemming from the fact that the same amount of current flows through all of the modules of each string, disabling individual module power maximization.

SolarEdge approaches the PV market in order to help “overcome the limitations of these current PV systems, by introducing a distributed power harvesting architecture that allow many additional benefits,” Handelsman states. “We offer module-level electronics that insulate the overall system from the many changes occurring in each module.”

The distributed power harvesting and monitoring system is composed of three elements: SolarEdge PowerBox, SolarEdge Inverter, and SolarEdge Monitoring.

Junction Boxes
The PowerBox has four key functions: optimizing power harvesting with module-level maximum power point tracking (MPPT), communicating performance data, maintaining a fixed string voltage, and turning off the voltage when safety is needed. This functionality gives the installer far greater flexibility to design an optimal system. Each PowerBox is powered by its own module, and does not require a separate power supply.

Module-level MPPT – A highly-optimized algorithm ensures each module is kept in MPPT, preventing power loss even in module mismatch or partial shading conditions. Module-level MPPT is faster and more responsive than tracking done at the inverter, and enables other benefits. The faster maximum power point tracker is able to follow changes in sun irradiance more precisely and efficiently than classic trackers. This agility ensures that no power is lost on partially cloudy days when changes in irradiance are frequent and fast.

Performance Tracking and Communication – Each PowerBox communicates with the inverter and the monitoring system, conveying a range of module-specific status indicators including: unique ID, amount of power produced, module voltage, current, and so forth. This telemetry is unique, as the data is transmitted over existing DC power lines, eliminating the need for additional wiring.

Fixed String Voltage – Traditional systems have held solar designers hostage to the very specific parameters of modules and inverters. The system must contain enough modules to meet the minimum voltage requirements of the inverter, yet not exceed its maximum permitted voltage, regardless of the system’s constantly changing environment. One of SolarEdge’s breakthroughs is that the PowerBoxes are able to maintain a fixed string voltage, and maintain it at the optimal point for DC/AC conversion by the inverter. Each PowerBox uses DC/DC conversion and all of them work together to ensure the string voltage is constant.

Inverter Options
A range of inverters are offered in order to meet the needs of both residential and commercial solar installations. Because the SolarEdge system distributes power harvesting and complex MPPT capabilities to each module, the inverter can be a fairly simple device. Features include:

Optimal Efficiency – The inverter does not need to track maximum power, so it does not lose power when the sun irradiance changes. Traditional inverter efficiency depends on input voltage, so these inverters do not always operate at their advertised efficiency.

With the power harvesting system, the inverter input voltage is always fixed. This constant input voltage guarantees that the inverter is always operating at the highest possible efficiency point, independent of string length or environmental conditions. Not only does the higher efficiency produce more power, it also reduces heat dissipation, lengthens component lifetime, and improves reliability.

High Reliability – In traditional systems, the voltage input to the inverter can fluctuate greatly with string length, temperature, and illumination of the modules, and can reach voltages as high as 1,000V. In the system, the input voltage is fixed and can be controlled to lower voltages. So, the inverter electronics operate under less stress and can be better de-rated to function well below their long-term damage states.

Advanced Communication Options – A built-in receiver for PowerBox transmissions allows reception of module level telemetries over the DC lines. Integrated Ethernet enables easy broadband connection to the monitoring server. Other communication options include ZigBee wireless communication, RS485 to permit communication between inverters, and RS232 for cellular modems in location where internet is unavailable.

Small Outdoor Enclosure – This allows easy installation in any location. The inverter’s compact and lightweight bracket-mounted design helps reduce installation time and effort.

Monitoring, Tracking
A comprehensive, hierarchal monitoring system that tracks system, string, and module-level performance is offered in two versions: fully integrated, for use in conjunction with the SolarEdge Power­Box, and a stand-alone monitoring package that will easily integrate with non-SolarEdge modules.

The SolarEdge Monitoring Portal tracks the technical and financial performance of one or more SolarEdge photovoltaic sites. The Portal provides accurate information about each individual module and about the system as a whole. This enables installers and site owners to quickly detect, pinpoint, and troubleshoot faults; efficiently manage maintenance operations; and analyze site profitability.

Smart algorithms continuously track the power, voltage, and current from all modules and inverters, as well as a range of statistical and meteorological indicators to detect sub-optimal performance or events that require intervention or maintenance.

The Monitoring Portal provides near real-time data, as well as aggregated, historical information. Further, the system provides diagnostics for comparative analysis, and a unique, guided utility to help identify the root-cause of any problem. The Portal automatically detects problems, issues status reports and alerts, and provides recommendations and suggested solutions. All the data is logged and can be securely reviewed and analyzed at any time from any location.These features enable installers, integrators, maintenance staff, and owners to improve the site performance and reduce maintenance costs by increasing system uptime and resolving faults more quickly.

The Portal is accessible via a standard Internet browser, and allows interaction with the PV system through a multi-tiered interface that is friendly enough for residential users and sophisticated enough to be of assistance to the most advanced installers and commercial site managers. The Portal does not require any installation or download of special plug-ins. Features of the Monitoring Portal include:

Accurate Fault Detection – Not only does the system provide comprehensive detail about performance, trends, and maintenance, but it incorporates artificial intelligence to provide context and analysis – helping installation and maintenance staff to quickly pinpoint the issues.

Fast Troubleshooting – Interactive charts and site layout maps make it easy for installers to ensure a system is functioning properly after installation, and quickly identify problems if they arise.

Customized Automatic Alerts – Users can identify the level of detail they wish to receive from the system. Alerts can be sent via email or through the Monitoring Portal.

Powerful Embedded Reporting Tools – The reporting summarizes all key data, including financial performance, energy production, and environmental benefits. Additionally, should a maintenance issue arise; the system can provide details about its financial impact.

Solar Field Maintenance Tools – Maintenance staff can create a consolidated view of all open issues for a given site or set of sites. Not only will SolarEdge provide this summary, but the system will also pinpoint the location of the related components at the site, and provide the history of each component’s previous failure events.

Maintenance History – A full history of activity at each site is automatically, maintained including current status and past incidents. This allows site owners/maintenance staff to effectively track the installation throughout its lifecycle.

Multi-Tiered Interface – Monitoring can be configured to control the information that is presented based on the credentials of the user. For example, an installer or integrator can manage a full view of all modules and alerts, while a homeowner is able to see basic performance information.

Increasing Flexibility
Benefits of the tiered system are brought to all players in the PV field. “Integrators and installers have more flexibility in designing a system; simpler system design ultimately lowers installation costs and time; installations are easily scalable; and there is full safety during installation and maintenance,” Handelsman explains. “Module manufacturers have fewer manufacturing limitations as there is no more temperature variance, cell mismatch, and manufacturing variations as well as no more need to stockpile specific modules for future maintenance needs – enabling speedy and efficient delivery of per customer systems.”

Additionally, system owners and maintenance providers see the value in the fact that the remote monitoring enables ease of monitoring at a lower cost, together with theft prevention mechanisms.

“The benefits of this solution from SolarEdge are being recognized within the industry, with numerous solar companies having entered into partnership with us,” Handelsman says. Some of those partners are BP Solar, Schott Solar, GE Energy, Gehrlicher Solar just to name a few, and it is these partnerships that are giving these architects of energy the solar edge.

SolarEdge Technologies
Palo Alto, CA