When considering off-grid renewable sources of energy to off grid power systems for your home, there are many options available. Solar power is the most obvious choice due to low cost and readily available products. But what happens when that first storm comes and the wind is blowing and the sun isn’t shining. Many homeowners are looking at supplementing their solar systems with a secondary input source. With the availability and decreasing cost of small, off-grid wind turbines that operate in even modest wind conditions, many people are choosing a hybrid approach.
Hybrid systems that incorporate both a solar panel system and wind turbine form a perfect complementary relationship with each compensating for the weaknesses of the other system. Where solar is best during the daytime, wind power works throughout the night. Where solar is better through the summer months, wind power can be better in winter months.
Solar power, though relatively inexpensive, is not always as reliable or efficient as possible in times of low sun. To generate power, solar panels must collect sunshine at sufficient intensity and at the right angle. This does not occur at night, or when it is cloudy and overcast. If snow covers the panels, power is not generated until the snow melts or the solar panels are cleaned off. This can cause charging issues in battery based systems that rely only on solar power where storms occur often or are in parts of the world where winters are extremely short. Adding wind power to a solar powered system also can lengthen battery life by reducing the depth and frequency of discharge. Since these off-grid systems are powered by wind when solar power is unavailable, it avoids drawing down the system’s batteries and increases battery life.
It is easy to see that wind power can complement solar in many instances because it often produces the most power precisely when solar power is reduced or unavailable, such as at night, in inclement weather, and during winter. Wind often blows during long winter nights and is, on average, actually stronger in inclement weather. During winter, average wind speed is highest, as is air density, both factors that contribute to wind generating more power when solar power tends to be least available. To enhance power reliability and build in redundancy, many off the grid homes are now being retrofitted with small, off-grid wind turbines. We recommend Primus.
Available in several models for areas with different wind speeds and climates, Primus’ turbines are designed to generate power at wind speeds as low as 6 mph, and can generate as much as 40 to 80 kWh a month per turbine depending on conditions. Each turbine measures about four (4’) feet in diameter, weighs about 13 pounds, and costs only around one thousand dollars per unit. A single wind turbine is able to provide an additional renewable energy source for charging batteries. If more power is required, several turbines can be combined together. Far from a new concept, small off-grid turbines from Primus have already been installed worldwide with over 150,000 units currently operating in the field.
The Primus AIR units are a suitable complement for nearly any off grid solar power systems where solar is being used. It is recommended that wind represent between 10% – 50% of the power generation capacity, depending on three variables:
Wind Resource: With solar accounting for 50% or more of the power generation capacity, the wind resource analysis should be focused on solar assistance, which is during winter time months when wind is at its peak. Most regions of the United States have sufficient wintertime winds to support most off-grid power needs.
Solar Resource (see solar resource map): In cloud-free locations at less than 35 degrees latitude, such as Arizona, wind will comprise a smaller percentage of total power generation (typically between 10% – 20%) since wintertime solar availability is high. Other locations such as the Great Lake region or Canada with shorter and/or cloudier wintertime months, off-grid systems should have much larger wind capacity (typically between 20% – 50%).
Load Specifics: Energy loads that are necessary in the wintertime and nighttime should have a much higher wind component. A prime example is hybrid lighting, where the load is increased in the wintertime (due to longer nights) and where energy is only needed during nighttime when wind power generation can occur and solar power generation cannot.
A hybrid solution of wind and solar can be adopted to meet energy needs. This process can be done relatively easy and in stages. Evaluating existing and anticipated power requirements should be reviewed in advance and the following factors taken into consideration:
Variety of Loads (appliances or energy consumption) lighting, refrigeration, small appliances
Peak Consumption: when, what and how often
Average Consumption: ongoing loads which are typically in use or on standby
Minimum consumption: loads being run all the time and consistently
AC or DC needs (i.e. may require additional auxiliary components)
Required availability – system as back up or supplementary
The expected output from Wind and PV depends very heavily on location, time of year and weather etc. designing the optimal solution requires other details to be assessed:
Location of install and descriptions of surrounding area and structures
Local wind and weather conditions / similarly local sun conditions
Other weather conditions to review:
A system that incorporates both WIND and SOLAR inputs will require a considerably smaller battery than one with sole power source of either option. Hybrid Solutions WIND/PV extend the life expectancy of a battery bank due to consistent flow of energy not allowing your system to drop below the recommended 50% depth of discharge. Hybrid Solutions WIND/PV allow for year round energy supply and consistency. The main focus is to know which resource you have more often and when (winter/summer & day /evening). This will allow you to outfit a system which maximizes on optimal energy supply as well as focusing on long-term life and usage of your solution and how each component contributes and when.
Primus is in the process of launching a new power sizing tool on our website. Compiled by AWS True Wind, we can now provide wind data and expected turbine output for each month of the year, and at specific tower heights, for any location worldwide. The Wind Resource Tool is 200 M resolution data at 10-15 M in tower height. All is needed is an address or a GPS/Data/Google Coordinates sent to Primus and they will produce a simple report on the wind resource and energy production of the AIR units.
You have free access to this sizing information on the Primus website: