Solar Energy and Micro-Grids

Clean, balanced, energy independence.

Solar energy is the great success of the renewable revolution, with cell efficacy doubling since 1990, now reaching almost 30% in mass production and up to 40% in academia. Installed solar power capacity is expected to exceed that of natural gas in 2026, and of coal by 2027, becoming the largest in the world, a 3x increase in installed capacity from 2022-2027. The global levelized cost of electricity from solar is now around 40% lower than coal and natural gas.

However, there is a fundamental problem with solar; the sun doesn’t shine for 24 hours a day. So, the key question is “How do we store energy in a home?”. The key answer is “In two batteries, one in your home, and the other is your EV”. The US ‘attach rate’ for storage capability sold with solar panels, has increased from 9.5% to 17.1% in only 18 months, and bi-directional on-board chargers (OBCs) are already available in the Nissan Leaf, Ford F-150 Lightning, Hyundai Ioniq 5, Kia EV6 and the Mitsubishi Outlander PHEV.

For extended periods in “off-grid” extreme north / south locations, standalone generators may be used to supplement energy input from solar, and potentially wind power.

Micro-inverters

In typical residential applications, a micro-inverter is attached to each panel and converts low-voltage DC to 50-60 Hz, 110 V AC power. Power ratings are increasing as panel efficacy improves, from 250-300W up to 450-500W. Companies such as Enphase have stated that they are moving from silicon to GaN to take advantage of higher switching frequencies and significant cost reductions, estimated at 25% per micro-inverter.

650 / 700 V GaN power ICs are used in micro-inverters, and the GaNFast 20-year warranty is critical for harsh application conditions of temperature and humidity.

DC Optimizer

An alternative method, for higher power systems, is to use DC optimizers between each panel, smoothing voltage and power to maintain efficiency, then feeding into a high-power string inverter. DC optimizers can use low-voltage (60-80 V) GaN.

String Inverters

String inverters aggregate the power from multiple DC-optimized groups of solar panels (‘strings’). Multiple strings of panels then connect to a single inverter where electricity is converted from DC to AC electricity.

SiC MOSFETs and diodes in the inverter and boost stages show a significant efficiency gain over legacy silicon power devices, while enabling fast switching frequencies to reduce system size, weight, and cost.

Company’s such as KATEK use GeneSiC MOSFETs in their ‘coolcept’ inverter topology to enable very high peak efficiency results of 98.6%, which means that less power loss has to be generated and dissipated to the environment.

The coolcept³-fleX inverters completely dispense with the electrolytic capacitors required for intermediate storage, which can influence the service life of an electronic device through possible drying out. When using coolcept³-fleX inverters, the plant operator therefore has the prospect of a long service life.

Battery Energy Storage System (BESS)

Approximately 30% of electrical usage happens during solar production hours. A Battery Energy Storage System (BESS) stores electricity from the sun (or other renewable energy sources) for later use, to reduce electricity costs, back-up unstable grids during blackouts, and support additional electrical demands.

A BESS consists of a battery module, battery management system (BMS), energy management system (EMS), and a power conversion system (PCS).

SiC MOSFETs and GaN power ICs are used in the inverter and buck-boost stages to convert AC to DC (from Grid to battery), DC-DC (from Solar to battery), and DC-AC (from battery to Grid).

Circuit Breaker Panel

A circuit breaker panel (or main electrical service panel) connects the electrical supply from the grid to the building internal electrical system.

Circuit breakers are switches inside the panel, that automatically switch-off when a circuit is overloaded – to prevent fire, electrocution, and other serious dangers.

Today, circuit breakers are electro-mechnical, which use moving parts and suffer lifetime degradation from arcing and ‘switch-bounce’.

Next generation solid-state circuit breakers (SSCBs) operate 100x faster than mechanical relays for faster protection.

No arcing and switch bounce provides higher reliability and longer lifetime.

Breakers can be digitally programmable and optimized, offer real-time power monitoring and communication.

SiC MOSFETs offer higher efficiency, lower EMI, improved surge current capability, and faster switching times compared to legacy silicon, for next generation solid-state circuit breakers.