How to Choose the Best Solar Grow Lights

Around 80% of Americans live in urban areas. As more people collect in large cities looking for work, we must come up with creative solutions for growing food and commodity crops within those cities and surrounding areas. Vertical farming and container farms are becoming more prevalent and the desire to grow ones own food indoors is increasing as our environment and food production needs change. Gone are the days of cheap fossil fuel and careless burning of energy resources. We need solutions and solar is a viable option.

We will be discussing solar grow lights and the variables you should consider before making a purchase. Energy usage, light spectrum, light intensity, generated heat, and size of your grow will all need to be balanced to achieve success with indoor solar powered lighting. With several light options to choose from we will go over types of lights, what to look for in a light, and additional things you should consider purchasing for your solar powered grow room.

Types of Solar Grower Lights

There are three main categories of light systems you can use for your Indoor solar greenhouse lights.

Fluorescent

This bulbs can be good for smaller grows, house plants, seedlings, or supplementary light. There are three bulb styles to choose from(T12, T8, and T5). The T denotes tube while the number indicates how many eighths of an inch the tubes diameter is. T12 lights, which are being phased out, generate electricity through electromagnetic induction, a less efficient method compared to the electronic circuitry In newer model lights.

The main difference between T8 and T5 lights is size. T5 lights are 40 percent smaller but can contain just as much or more light energy than T8 fluorescents. T5 lights are the most expensive option but will give you the best results. These lights are pretty energy efficient but won’t work for larger grows or large flowering plants.

LED

This lights are compact, safe, use less electricity, have a greater light intensity, and generate less heat compared to more traditional lighting options. NASA was a pioneer in LED use as a way to grow plants in space and induce alertness in astronauts. We are able to control the light spectrum emitted from the LED by altering the material they are made of, enabling creation of light in the photosynthetic spectrum while reducing other wave lengths.

This reduces power needed and heat produced while still exceeding performance of other light systems. Another large benefit of LEDs over more powerful HID bulbs are the ability to use a varying light spectrum to encourage the growth you want. LED style lighting would be my first choice for a solar powered grow. LEDs are an expensive initial investment but will pay themselves off in the long term. With the right expectations and planning, off grid LED lighting can be possible

High intensity discharge, or HID

This grow lights are extremely powerful but are expensive to run, hot, and power hungry. They are great for plants that need high intensity light to flower and fruit and are best for commercial growers who have a larger budget and aren’t as concerned with energy usage.

They come in two varieties that are usually used in conjunction with one another. High pressure sodium(HPS) bulbs produce low spectrum(red) light used in the flowering of plants. Metal halide(MH) bulbs, with their high spectrum(blue) light are used for vegetative growth. Both vegetative and bloom spectrum lighting must be used for the best results. Keep in mind you need to purchase two sets of bulbs and possibly two different ballasts, depending on model chosen, when using this system.

Vegetative vs Bloom

When growing with indoor grow lamps farmers must vary light spectrum and day length to get the desired growth from their plants. The growth before flowering is considered the vegetative stage and is controlled by day length.. For example, with cannabis, lights should be lit for around 18 hours in a more blue spectrum light to encourage vegetative growth.

The second phase is considered the bloom phase, where the plant will produce flowers and fruit. This stage of growth requires longer nights compared to the vegetative stage, usually a 12/12 hour split, with a light geared more toward the red spectrum.

Light Spectrum

Light from the sun contains the entire spectrum from ultraviolet(UV) to infrared. Plant biologists consider 400nm(red)- 700nm(blue) wavelength light available to plants for photosynthesis. Grow lights that cover this full spectrum will give you the best growing results. Some light models have an available switch that can set the light to either vegetative or bloom growth.  

This is a useful feature as it reduces the need for additional lights while improving grow quality. Look for spectroradiometric data from manufacturers that measures energy in watts per wavelength. Utilizing data will allow you to compare wave lengths of light available to your plants.

Light Intensity

Different plants need different light intensities. Even single plants require different intensities during different growth stages. Light intensity given off by grow lights is measured in watts. A more specific measurement is Photosynthetic photon flux density, or PPFD, measured in μMol/m2/s.

This measurement tells you the PAR(photosynthetically available radiation) usable for plant growth, or the number of available light particles hitting a square meter area in one second. Full sun provides approximately 2000 μMol/m2/s. Intensity can be varied by purchasing a more powerful light or moving the light closer to your plants.

Duration (Light Cycles)

As plants progress through their growing cycle we can influence biological processes such as the growth rate and the setting of buds/fruit by altering light cycles. A light cycle is simply how much light time and dark time the plant gets daily. When a plant is exposed to light radiation it is able to chemically convert this energy, along with carbon dioxide and water, into oxygen and glucose.

This energy is stored in the plants and used for cellular respiration. Cellular respiration occurs during dark hours. The plant chemically converts its stored glucose into carbon dioxide, water, and ATP energy molecules used for plant growth and reproduction.

Energy Usage

The amount of energy required to grow plants is immense and you must consider this when choosing which light system to use. Power needs will change as the plants progress through their growth cycle and the farmer starts altering day length and light spectrum.

LED lights will use the least amount of energy, while HID lighting will use the most. Fluorescent lighting is also efficient and can be good for small grows and supplementary light. I suggest using a LED grow lights system as they are energy efficient and can deliver a great product, saving you money in the long run.

Short vs Long Day Plants

Different varieties of plants have differing light needs. Short day plants only produce flowers when day length is less than about 12 hours. These include many spring and fall flowering plants like poinsettias and chrysanthemums. Long day plants on the other hand, require more than 12 hours of sunlight to enter bloom.

Summer crops like lettuce, spinach, potatoes, and California poppies bloom when the days are long. Other plants like tomatoes, corn, cucumbers, and some strawberries are considered day-neutral. These plants form flowers regardless of day length. Keeping day lengths in mind can help you choose crops that use less light, saving energy.

Installation and Additional Purchase Considerations

When installing your new grow lights you will need a way to hang the lights above your plants. You will also need a way to raise the fixtures as the plant grows in height. This can be done with a pulley system or a chain hung from the ceiling, allowing you to hang the light from different chain links as the plant grows.

You should consider purchasing a timer to control light cycles along with some form of ventilation to keep air moving. For a full solar light setup you’ll need a solar panel to collect energy from the sun, a MPPT(maximum power point tracking) controller to optimize amperage to the battery, a deep cycle battery to store energy and prevent damage from excessive discharge, a power inverter to convert DC to AC current, and of course your grow light. Greenhouse LED grow lights can be used to supplement sunshine for needy plants during short and cloudy winter days