Solar Power

Introduction

There are many forms of energy produced from solar sources; however here we focus on Photovoltaic Solar – the most realistic option for homeowners for producing their own electricity. Other forms of solar include Concentrated Solar, using heat from the sun to heat a transfer medium (or fluid) for use in conventional thermal power generation and the use of solar water heating to heat buildings, homes, domestic hot water and swimming pools.

Photovoltaic Solar Systems

Solar power produced directly from sunlight is known as Photovoltaic or PV. Using semiconductor technology PV systems convert sunlight directly into electricity.

PV Systems typically vary in configuration depending on the need they are serving. All consist of a PV Array to convert sunlight into DC power and an Inverter to convert the DC to AC power for use in a home, building or commercial application.  There are three main types of PV Solar Systems:

Grid Dependent Solar PV Systems rely on being interconnected to the power grid, don’t use a battery backup system and can export energy back into the grid.

Grid Interactive Solar PV Systems utilize a battery backup system and a controller to store excess solar energy instead of exporting it back to the grid.

Grid Independent Solar PV Systems utilize a battery backup system and a controller that will manage the storing of excess PV energy and control the operation of a standby diesel or propane power generator.

PV Cells, Modules and Panels

The PV Cell is the most discrete component of the PV System. PV Cells may be round or square and are usually 40 sq cm in area. One cell will produce 0.5 volts DC. Organized as PV Modules, as many as 36 cells are connected in series to increase the voltage to a more useful 18 volts DC that can be used in charging 12 volt batteries on in operating DC power devices.

PV Modules are typically connected in parallel, as a PV Panel, to increase power output. PV Panels can vary in size depending on application requirements, however typical PV Panels range from 350W to 425W in output depending on efficiency. PV Panel’s are pre-wired and packaged from the factory. The size and weight of a PV Panel is often dependant on what two workers can effectively manage to install on roofs or other surfaces. One or more PV Panels, once installed, form a PV Array.

Panel & Array Installation

PV Arrays are often “Standoff-Mounted” to roof surfaces, parallel to the roof surface with an air gap between the array and the roof to allow for cooling.  Residential PV Arrays are sometimes installed as patio covers as an alternative to roof installations and to provide shade for the patio.  Other common methods of installation include Rack-Mounted PV Arrays.  Purpose built racks support the arrays and some pole mount systems can track the sun’s movements to improve overall efficiency.

Standoff-Mounted PV Array

Rack & Pole Mounted PV Arrays

Micro Inverter Technology

A significant evolution in the solar industry is the use of Micro Inverters.  A Micro Inverters is typically connected to each panel converting the output from DC to AC for use in the home and then each is connected to a cable that brings the output from each panel to the main circuit panel.

Micro Inverters eliminate the inverter as a single failure point.  When a Micro Inverter fails there is only a loss of one panel’s output.  With older single inverters for a series of panels, an inverter failure would shutdown all solar production.  

 
Micro Inverters also lend themselves to expansion.  As you decide to increase your solar production you only need to add one with each panel.

Incoming Solar Irradiation

Important to the effectiveness of PV power generation is the overall level of incoming “Solar Irradiation”.  Solar Irradiation is the measure of the solar energy that arrives to a specific location on the earth over a specific period of time interval.  Solar Irradiation is measured in kWh/m2 (of Array) on a daily or annual basis.

Solar Irradiation is affected by location on the earth; weather patterns, PV array tilt or inclination to the sun and whether the array is stationary or can track the sun’s position.

The following diagram depicts the long term average Solar Irradiation in kWh/m2 for a horizontally mounted stationary PV Array in Mexico.

Based on the above Solar Irradiation levels, a south facing horizontal stationary PV array in Cabo San Lucas comprised of 6 385 Watt panels with an area of 2 m2 each that are 19.42% efficient would occupy 12 m2 and would produce in the order of 5,600 kWh annually. 

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6.6 kWh/m2 per day X 365 days X 2 m2 per panel X 6 panels X  19.42% = 5,614 kWh

Solar System Prices and Economics

Current economics

Off-grid Solar installations typically compete very well with grid sourced energy supplies based on economics and ease of maintenance.  Where connections to grid systems are costly (or sometimes non-existent) and self-generation must be considered, Solar is becoming an ever-increasing choice with a significantly growing share of the off-grid market.

Alternately grid connected Solar was, for many years, uncompetitive with conventional generation sources – fossil fuelled, nuclear and hydro. This has changed over the last decade with steadily declining costs for Solar PV systems.  Grid connected solar has become very reasonable when compared to the high price of electricity from CFE on the dreaded DAC Rate.

Typical CFE rates

Typically electricity from CFE in the regular Tariff in Cabo (“1C”) runs US 10¢ per kWh to US 14¢ per kWh.  On the DAC Rate this almost doubles to US 17¢ per kWh to US 24¢ per kWh.  

Typical solar costs

Installed PV solar costs in the Baja run between US 12¢ per kWh to US 14¢ per kWh based on estimated solar production from solar installers and a 20 year panel life span.  These solar production numbers tend to be conservative and based theoretical production output (noted above) the costs would be US 8¢ per kWh to US 10¢ per kWh.  Solar is an attractive investment when faced with the much higher costs of being on the DAC Rate.

Factors affecting your solar investment

The electricity industry in Mexico is undergoing transition to deregulation of electricity generation.  Transmission and distribution functions will remain part of CFE.  The current plans are for only industrial and large commercial customers to be allowed to choose an alternative provider to CFE for their electricity.   Tariff structures in other jurisdictions that have deregulated have evolved to reflect delivery charges (use of transmission and distribution systems) being a largely fixed charge.  Where these changes have occurred solar economics has suffered as a result.  Previous delivery charges were kWh based which allowed solar installations to avoid these charges.   At the moment all CFE residential tariffs are kWh based which allows a homeowner to offset all consumption and have a zero bill.

 

Considering Solar? We can help!
MXelectricity can help you understand how much solar generation you will need to make the best investment.  Contact Us.