Early Discovery and Innovation

In 1839 French physicist Alexandre-Edmond Becquerel discovered that an electrical charge resulted from the absorption of sunlight by a conductive material. American inventor Charles Fritts used Becquerel’s discovery to create the first solar cell in 1883. Research and development in solar cell technology increased after the launch of the Soviet Sputnik satellite in October 1957. The space race spawned a competitive rivalry between American and Russian scientists to build lighter and longer-life spacecrafts to dominate control of outer-space. Discovery and innovation in material science, microelectronics and solar power systems were critical considerations in spacecraft design and leadership.

Fabrication of materials with electrical properties focused attention on germanium and silicon as semiconductors of electrical charges. Germanium provides higher electrical efficiency than silicon but is not as efficient as silicon at higher temperatures and a scarcer, costly material to manufacture. In 1954 former Bell Labs scientists working for Texas Instruments designed the first transistor using silicon to replace germanium-based transistors as the material of choice to design and build microelectronic devices. Silicon was available in greater abundance and lower cost than germanium. Silicon could also be manufactured in higher quantities at significantly lower unit cost and was more tolerant to handling and high temperature applications than germanium microelectronic devices.

While silicon ruled terrestrial solar power applications germanium remained the preferred material for solar cells used in spacecraft. The higher cost trade-off of germanium was balanced by higher efficient solar cells that allowed smaller and lighter onboard solar power systems that lowered the weight and extended the useful life of these significantly expensive spacecraft. Similar environmental and financial constraints did not apply to land based solar power systems that were best suited to less-efficient but materially lower-cost silicon solar cells and modules.

Widespread early use of silicon semiconductors stimulated manufacturing innovations. Solar cell production quantities and quality increased. Encapsulation methods improved to increase the useful life and bankability of lower-cost more reliable solar power modules. The price of silicon ingots declined significantly since 2005 to make silicon-based solar cells less expensive to produce while the capital costs of tools to manufacture silicon-based solar modules remain less expensive than tools used to manufacture Thin Film solar modules.  A solar module is a collection of solar cells encapsulated in a rigid rectangular vacuum-sealed glass-top package.

Thin Film solar cell technology is an alternative solar cell and module technology. Layers of photo-sensitive chemicals are deposited onto a thin film substrate that is encapsulated into a solar module. Thin Film (TF) solar modules have not (1Q2011) achieved competitive kilowatt hour (cost/kWh) production efficiency compared to mono-crystalline silicon (mono-Si) and multi-crystalline silicon (poly-Si) solar modules. 

The cost-effectiveness of mono-Si and poly-Si modules is expected to increase as production techniques and module efficiency improve. The price and efficiency per watt of poly-Si modules are marginally less than mono-Si modules.

Electricity from Photons

Sunlight carries photons that are absorbed by solar cells made of semi-conductor material. The top and bottom of a silicon solar cell is doped with a chemical of different opposing atomic structure and electrical charge. The top thinner layer of an n-type solar cell has a dominant negative charge and a dominant positive charge on the bottom thicker layer. 

A conductive dye is printed in a finger-like pattern on the sun-facing negative charge side of the solar cell to increase reception and absorption of photons.  A pair of  conductors called busbars carry the current from the solar cell’s finger-like photon receptors to serially adjacent solar cells.

Photons from sunlight absorbed into solar cells dislodge atomic particles from normal state. Disoriented negatively charged electrons find resistance reconnecting with positively charged atomic holes. An invisible band gap separates the top and bottom of a solar cell that forms a resistive barrier to reconnection of electrons and holes.

Metal busbars bridge negative and positive sides of adjacent solar cells in series and provide an efficient path for electricity transmission between solar cells. Aluminum backing seals the bottom of each solar cell to contain electrical charge within each solar cell. 

The reconnection of dislodged electrons with available holes generates an electrical current and voltage. The product of a solar cell’s current and voltage results in electricity measured in direct current (DC) watt-hours which an inverter converts to alternating current (AC) watt-hours to support an AC load or transmission to the AC grid.  

Solar Modules, Arrays and Balance of Systems

A solar module encapsulates 60 or 72 solar cells, usually in six columns of 10 or 12 solar cells. The sum of each cell’s voltage carried by the current across the solar cells determines the electrical power or watt-hours (Wh) that the solar module can produce.  Solar modules are assembled into solar arrays that make-up the energy receivers and conductors of direct current (DC) electricity. 

An inverter is an electrical conversion and power management device that is an integral component of all grid-tied solar power systems. The inverter converts direct current (DC) electricity to alternating current (AC) electricity standards required for transmission to the AC electrical grid. The inverter’s durability, capacity and efficiency to optimize and manage DC to AC electricity power transmission is an important determinant to investment pay-back and rate of return of the solar power system.

The inverter, racking, wiring, junction/disconnect boxes and wiring/grounding chases are referred to as the Balance of Systems (BOS). Electrical grounding devices/wiring and racking systems protect and support the solar array on rooftops or on ground-mounted projects. Wiring delivers the electircal power generated from the solar array to the inverter and to the electrical grid. Junction boxes are conduits that consolidate wiring from modules to the inverter. Disconnets are devices that shut-down DC and AC transmission of electricity within the solar power system for maintenance or emergency purposes.

Solar power system generation is increased by fixed slope racking that position solar arrays to receive higher duration of direct sunshine based on the latitude of the project site.  Sun trackers provide additional optimization using single or dual-axial monitoring and mechanical devices to adjust the solar array’s tilt angle and orientation to receive sunlight through daylight hours and seasonal variation of solar inclination in relation to the latitude of the project site.

Peak Sun Hours

The pay-back and investment return from a solar power system located at a particular site requires due diligent assessment of several parameters. Sunlight rises at dawn in the east and declines in the west at dusk as the earth spins before the sun and daylight turns to darkness.  Solar power generation occurs only when there is direct and indirect or diffusive sunlight. A high density of photons delivered over a long duration of time results in higher peak sun hours that offers greater solar power generation opportunity. Seasonal changes impact on the duration of peak sun hours as the solar window expands and shrinks between the summer (June 21st) and winter (Dec. 21st) solstices.

Solar power generation systems have a long history in supplying space satellite power requirements.  Early solar power systems continue in service after 28 years.  Solar module manufacturers offer 25 year limited warranties. Selection of quality solar power system components and contractors is a critical success factor to ensure reliable optimal electricity generation over several decades.

Ontario’s Feed in Tariff Program

The Green Energy Act regulations directed the Ontario Power Authority (OPA) to buy electricity from renewable energy sources based on prices or tariffs guaranteed for 20 years in the OPA contract or Power Purchase Agreement. The tariff paid for solar electricity transmitted to electrical grid is based on the energy source (solar or wind), site location (roof-mount or ground-mount) and the inverter’s kilowatt (kW) or nameplate capacity.

There are two Ontario feed in tariff (FIT) programs. The Micro-FIT program is designed for smaller power generators of 10 kW or less. The FIT program is available for power generators greater than 10 kW of nameplate capacity. The FIT market is suitable for most commercial, industrial and institutional rooftop owners. 

Suncharge offers solar power lease advice and representation on behalf of property owners and developers.