Tigo Energy™ power electronics system for modules

Tigo Energy has developed a power electronics system for PV solar projects which distributes key elements of instrumentation, control and maximum power point tracking to the module.  The system provides optimal power harvest from each module while not introducing additional conversion loss or significant cost increases relative to today’s centralized BOS electronics.  By placing a small amount of electronics on each panel, Tigo Energy eliminates the system impact of underperforming modules (made weaker by high temperature; dust & debris; aging; clouds; or shade) and thus harvests up to 20% additional energy.  This significantly reduces levelized cost of energy (LCOE) and project payback period.

Information (voltage, current, power, temperature, irradiance, etc.) gathered at the module is transmitted to a database where it can be accessed by a suite of analytic, alerting, metering and maintenance applications.  An intuitive web-based UI provides a comprehensive view of system performance which scales to the needs of installers, residential owners, and utility scale operators.  The unprecedented level of information and guidance can lead to significant reductions in operating and maintenance (O&M) expenses.

Tigo Energy is also able to address many of the safety issues that confront solar installations.  Today’s serial interconnection of panels ensures that when the sun is shining there is the potential of very high voltage (above 400 volts) on the cables – even when the DC shutoff is in the “off” position.  The hazard to installers, maintenance personnel and firefighters is evident.  The Tigo Energy system can disconnect each panel from the string, limiting the exposure to only the Voc of a single panel (usually <40v). In many cases this will streamline the permitting process and provide peace-of-mind to the home or business owner.

DESCRIPTION

Today’s PV systems are typically comprised of modules (panels) serially connected to one another in strings until the voltage maximum is met (600V or 1kV as restricted by the US and Europe respectively).  For larger installations, several of these strings are connected in parallel to form an array.  Because of the serial and parallel interconnection, power output of the each module in the array will be affected by the weakest modules.  Therefore it is important for system to be comprised of PV modules that perform identically.  Significant effort is expended by the value chain to match the modules (in type, power rating and manufacturer), orient them in the same direction, and ensure co-planarity thus minimizing output variability at installation.  This increases the cost of module production and installation while greatly reducing the options for rooftop hosts of solar systems.  Furthermore, environmental effects such as uneven soiling, temperature variations, settling or other slight differences in orientation, and property migration of silicon become evident within weeks leading to significant losses due to increasing mismatch.  These effects compound over time through the life of the project (20-25 years).

Today’s central or string inverters perform the DC to AC conversion necessary to deposit energy production onto the grid.  The inverter also attempts to keep the array (or string) at the highest power output possible.  To find the point at which the entire system can produce the maximum power at the current solar irradiance point, the inverter usually applies a “trial & error” algorithm which adjusts its current draw on the system.  By measuring the new DC power input, the inverter will determine whether to continue the adjustment in the same direction or reverse course.  This process is constantly looking for the peak power point but rarely finds the system working at this point (only instantaneously during transitions).  There are many variants of the simple algorithm but with input data limited to system DC voltage and current, all have limited accuracy.  The task becomes significantly more complex during times of changing irradiance (ex. cloud cover, shading) as each module’s maximum power point is dynamically moving.  System stabilization may take several minutes after a cloud has passed leading to high losses.  Because each module has a series of by-pass diodes, a significantly under-performing module will be “turned off” when the current drawn from the inverter exceeds its ability to provide power.

Tigo Energy’s technology directly addresses production losses due to module performance mismatch and central/string power point tracking methods by placing a small electronics footprint on each module.  Module and environmental characteristics are determined through instrumentation, maximum power point is calculated, and each module provides the most power output possible.  The system can react instantaneously to irradiance changes as each module adjusts quickly and independently to maintain maximum contribution.  

Much of the production losses occur as environmental factors and system wear take their toll on the PV array.  Understanding the time based degradation of the system requires an ability to measure the power output over long periods and correlate this data to expectations from seasonal irradiance and weather conditions.  There are many system monitoring solutions available today measuring at the inverter, but from this information it is extremely difficult to detect reoccurring power losses caused by gradual soiling, shading, heat patterns, or module defects – much less pinpoint the offending modules so that proactive maintenance can be preformed.  Broken or substantially degraded modules will remain undetected and contribute to the permanent output loss of the system.

Tigo Energy’s panel electronics communicate module characteristics to the Tigo Energy Management Unit which computes operating point of each module using both module and array data.  This data is also provided to a data base (the Management Unit also provides a “gateway” function) which feeds the Tigo Energy “Micro Manager” application suite.  Application modules analyze long term array performance, flag severely underperforming or broken modules, and provide reports for targeted maintenance actions.  This allows project owners to lower O&M costs, exercise warrantee replacements and keep the system running at peak efficiency through the life of the project.  The granularity of project visibility has never before been available in a cost-effective implementation. 

In California and other fire-prone regions, emergency services personnel have raised concerns that today’s solar roof-top installations present a danger when extinguishing a structural fire.  This hazard extends to homeowners or maintenance professionals who choose to service an installation.  Even after the DC disconnect is activated, the modules continue to generate power as long as there is sufficient insolation.  Due to the serial connectivity of the string, each module and cable can be carrying a lethal level of voltage (well in excess of 400V).  The potential for arcing and electrocution from applying water or cutting through a module is an impediment to addressing a burning structure. To avoid such a scenario, local building authorities are slowing approvals and requiring expensive “quick-release” racking systems which further burden the cost of solar installations.   

Tigo Energy’s panel electronics include circuitry which is able to “disconnect” each module from the interconnecting cabling, deactivating the array and limiting exposure to the open circuit voltage of an individual module.  When not connected to the Management Unit, the electronics default to the “off” state, also creating a safe environment during installation.  When the system is functional, the array may be deactivated by a button on the Management Unit or remotely through the web-based management console. 

The Tigo Energy system consists of the following elements …

Tigo Energy Link Module Unit (LMU) - one unit is installed per module or grouping of modules.  The unit contains instrumentation and control logic, power-line communications, and filtering. 

Management Unit - one unit is installed per project with the option of a second for system redundancy.  The unit communicates with the panel electronics via the DC power line, provides control function for the link module units, and serves as a gateway to the Data Center.  The management unit is pre-configured with Ethernet access and can ship with optional wifi or cellular communication modules.  The management unit is also capable of reading performance input from the inverter and can serve as a qualified monitoring tool for legacy installations.
 
Power Conditioner - one simplified inverter is installed per project up to 500kW and provides the DC/AC conversion function.  Through a variety of partnerships a wide array of capacities (versions from 2.5kW to 500kW) and geographic requirements are provided.

Tigo Energy Intelligent Data Center - one server (or hosted partition) per customer which retains all data gathered from the panel-level monitoring of each customer installation.
Tigo Energy “MicroManager” software applications – the software provides panel level performance monitoring, analytics, alerting, real time maintenance tool, pre-sales project planning, and remote system control.  Applications may be added to the suite based on market requirements. The suite is user configurable and can provide views appropriate for residential consumers, installers, power plant operators, emergency services, etc.  All applications are web-based and provided as SaaS, accessible through tigoenergy.com through secure methods.

INNOVATIVE ASPECT

1.)    Tigo Energy is not a micro-inverter – Tigo Energy has focused on addressing aspects of the system that contribute to inefficiency  – MPPT, module interdependency, performance visibility and safety.  AC power conversion is implemented very effectively by a host of manufacturers with excellent conversion rates and is not a weak link of today’s solutions [current reliability issues in inverters are typically related to the high power electrolytic capacitors – and less due to the AC bridge electronics].  By keeping the electronics footprint on the module very small (no DC to AC), the solution provides simple installation (and seamless integration into module J-Box), enhanced reliability, low cost, and scalability (performance and cost) from residential to utility.
2.)    Tigo Energy provides a similar system cost structure to today’s projects – Tigo Energy’s approach is a “distribution” of existing components rather than the “addition” of system elements.  This allows Tigo Energy to provide performance upside up to 20% with the same capital expense of a traditional solution.  Greater output, improved reliability, streamlined installation, and more effective O&M all mean lower LCOE on the first day of project activation.
3.)    Tigo Energy does not increase conversion losses in the system – the solution does not rely exclusively on DC/DC conversion for MPPT.
4.)    Tigo Energy augments the existing PV solar value chain as part of the ecosystem – Tigo Energy brings innovative technology to enhance PV (including CPV) solar installations and is working with many industry leaders to optimize the system solution.  Tigo Energy’s business success is not predicated on the disappearance of incumbents.  Tigo Energy will make contributions with many others to reduce the LCOE for PV solar and thus keep the market growing exponentially.

BENEFITS

Utility scale – PV solar programs are typically developed and operated by a group of interests that finance, build, operate and maintain projects from 50kW to those of multiple megawatt.  Participants may include investment banks (or those arranging project financing); engineering / procurement / construction (EPC) contractors; system owners responsible for operation and maintenance (O&M); and ultimately public or investor owned utilities who purchase and resell the power generated.  In some cases, companies (for example Sun Edison) may play multiple roles.  Each participant in the project has the objective to achieve the lowest LCOE to optimize the return of the project.  Tigo Energy’s solution helps in meeting this objective by offering:
·    In a well architected and regularly maintained system (2x per year) Tigo Energy equipment will typically return 4 to 8% incremental power output through the life of the system.  Financial estimates indicate that an increase of 6% harvest can increase the project IRR by 20 basis points often providing 30-40% increase in returns.  By potentially offsetting today’s increased cost-of-capital, the Tigo Energy solution can place non-viable projects into profitable operation.
·    Very low or no incremental cost relative to traditional system implementation such that economic value of additional power generation can be realized early in the project lifecycle.   Additional costs savings are available by eliminating the increased BOS costs associated with thin-film installations.
·    A low cost retrofit option provides improvement for existing underperforming projects.
·    Streamlined system design assist the EPC with greater layout flexibility, reduced BOS components (combining), and faster installation.
·    The monitoring console with module level granularity provides detailed visibility, analytics and diagnostics so the project can be kept at peak operation throughout its lifecycle.  By understanding the performance levels of each system component, warrantees can be quickly and effectively exercised.
·    An environment where there is no longer a need to closely match module characteristics to optimize performance.  Therefore, a variety of module suppliers and types can be utilized in the initial project design.  There is also no need to inventory modules for future replacement.  Modules can be replaced with the most cost effective wattage output at any particular time in the project lifecycle.
·    On-demand reports help maintenance crews target problem areas and ignore those which are operating well.  This selective activity can greatly reduce time in the field and O&M costs. 

Wholesalers – this important link in the residential and small/medium size commercial value chain provides valuable stocking, forward / reverse supply logistics, short-term finance terms, system integration, component interoperability and performance testing, and installer training.   A wholesaler will often have reach into dedicated, authorized or franchised installer networks which take advice on component and brand selection.  Tigo Energy offers value to the wholesale channel by:
·    Providing a new, innovative product for differentiation to their installer base.
·    Enabling better substantiation for warrantee services and vendor side reverse logistics on all system components through the monitoring tool.
·    Enhancing warrantee length on BOS electronics.
·    Enabling additional value-add services such as the pre-configuration of the Tigo Energy LMU onto PV modules.

Installers – these local, regional and sometimes national system installers are the front line to residential and small / medium commercial customers.  The installer promotes and markets systems; plans and quotes projects; procures all system components; secures approvals and permits; installs; interfaces to utilities for grid-tying; handles federal, state and local incentive applications, and may provide financing.  After project completion, quality installers maintain customer relationships to field questions, provide service and warrantee coverage.  Tigo Energy enhances the installers’ business by:
·    Offering an innovative technology which can differentiate their product proposal by offering greater energy production and lowering the cost per kilowatt hour generated.
·    Providing more granular and visually compelling monitoring software than currently available, allowing the consumer to access the data in near real-time at any web enabled PC.
·    Simplifying on-site installation time and reducing BOS system components (assuming pre-configuration with PV module by wholesaler or module junction box integration).
·    Increasing the number of addressable roof-top hosts for economically viable solar installations by enabling module placement in slightly shaded areas or alternative orientations (SE or SW planes).
·    Supplying a pre-sales planning application which automatically places modules on a satellite image of residential or commercial prospect and generates potential system statistics.  This tool can generate collateral for customized mass solicitation and reduce at least one pre-sales site visit.
·    Including software which proactively alerts installer of system problems and long term production statistics (to module level granularity).  This can be used to create a value-add maintenance programs, enhance longer term revenue streams, and more effectively service warrantee work.    

Residential consumers – Tigo Energy brings value to the owners of residential systems by:
·    Generating 10 to 20% more annual system output for the same initial cost of a traditionally configured PV installation.  The consumer will potentially qualify for greater incentives in performance-based schemes (such as CSI). 
·    Providing software tools so they may fully understand the long-term performance of the system, the economic value returned, and how to keep it at optimal output through its lifetime. 
·    Delivering password protected Web access giving the consumer additional tools to highlight their green project and eco-awareness to friends and associates away from home.
·    Providing peace-of-mind that in an emergency situation the array can be deactivated for rapid, safe and effective fire suppression efforts.

Building Integrated Photovoltaic (BIPV) – With the increasing interest in LEED standards for green construction, the desire to integrate PV into traditional building materials is becoming commonplace.  With the installation of solar panels on the face and roof of large building structures, urban infill generation can be expanded, reducing capacity expansion requirements for the grid and reducing the carbon footprint of these large facilities.  In curtain wall applications, vast amounts of existing and new opaque building surface are available for PV placement.  As the incremental costs of substituting PV for relatively expensive tempered glass lies only in the PV material cost itself, they can be constructed in a cost-effective manner.  However, power generation from such applications is hindered significantly by the inability to align orientation; variability in string lengths and panel dimensions; and excessive shading.  Tigo Energy unlocks the potential of this application by:
·    Eliminating the impact of underperforming modules on the rest of the array thus maximizing power production.
·    Power harvesting at the module level, which enables the use of a variety of module sizes and shapes thus improving aesthetics.
·    Minimizing module level footprint for flexible placement of electronics and enhanced reliability within the curtain wall.
·    Providing galvanic isolation at each panel.
·    Enabling the power bus to be completely deactivated for day-time maintenance or in case of fire.
·    Providing visually compelling monitoring software which can be displayed in the building lobby to enhance the green image of the facility owner.

ADDITIONAL INFORMATION:

N.B. Tigo Energy is happy to provide judges with access to data from several installations dating back to April 2007, through a username and password to the tigoenergy.com installation portal.  Password will be provided in separate communication.