Reaching grid parity has long been the goal of manufacturers. While the solar industry has faced a number of challenges to that end, a handful of new adhesive/sealant technologies may help to attain it.
A variety of dispensing equipment allows manufacturers to choose the best material for both production processing and durable finished goods.
What is Grid Parity?
In simple terms, grid parity means that the prime cost of
solar energy is equal to the prime cost of generating fossil fuel energy. It’s
not the price of operating solar power production, but the total cost -
production, labor, initial cost of system components, installation, operation,
maintenance, etc.- that is invested to generate a certain amount of energy.
Today, prime costs of fossil fuel are approximately 4¢/kWh, while prime costs
for photovoltaic energy are in the 20-80¢/kWh range when spread over a
lifetime. The ultimate goal is to have these lines cross. One way to achieve
this is to focus on manufacturing more efficient solar modules. However, reducing
production and material costs is another major - and necessary - strategy in
achieving parity. Thanks to several new adhesive and sealant application
technologies, that part of the challenge is becoming attainable.
In-line, automated application of sealants for frames and backrails
allows the purchase of cost-efficient, larger-size sealant containers
and improves cycle times.
Solar Manufacturing Today
Today’s solar-panel manufacturers are in a precarious
position. Although they currently face a slowdown in demand due to the global
economic crisis, demand is expected to recover soon, thanks to new incentive
programs currently in place worldwide. With lower demand, pricing pressure
increases. This means manufacturers need new automated technologies that can
help them to stay competitive by reducing costs and increasing production
speed. These technologies will also help as manufacturers prepare for the
growth in demand predicted for the near future.
Realizing grid parity and empowering solar manufacturers to achieve business
success requires technologies that overcome a combination of manufacturing
Solar panel manufacturing currently involves intensive manual labor at several
stages of the production process. By automating or semi-automating these steps,
new technology can reduce production costs and significantly increase product
quality. Furthermore, there is a consistency inherent to automated processes
that cannot be matched by manual production.
Limited processing technologies have forced manufacturers to use less efficient
or effective materials. Currently, manufacturers rely heavily on ambient
silicone materials for sealing. These single-component (1K) adhesives cure
slowly, which inhibits production speed and increases work-in-process.
Manufacturers need technologies that enable the use of smarter materials,
including two-component (2K), reactive or hot-melt adhesives, which would allow
them to work faster and/or use less material.
New technologies enable systems to process larger material bundles, which
allows manufacturers to source materials more cost-effectively and increase machine
Crystalline vs. Thin Film Modules
While traditional crystalline solar modules can greatly benefit from new
production technologies, the newer thin-film modules offer especially promising
parity possibilities. This is due to several qualities: they use only a
fragment of the photovoltaic material that crystalline modules use; glass, used
for the panel’s back and front, is an inexpensive resource; and the thin film
module design usually makes manufacturing easier to scale and automate.
Traditional vs. Smarter Materials
Enabling processing of a wider variety of adhesive/sealants
allows manufacturers to select the best possible materials for their
operations. Certain “smarter” materials achieve their results faster, often
using less sealant, which can decrease costs and increase throughput and
The solar industry has been using ambient temperature materials almost
exclusively, including ambient-cure adhesive/sealants or tapes. However,
hot-applied and reactive materials have enormous potential for solar panel
Materials used for solar manufacturing must:
- Provide a moisture barrier.
- Not conduct electricity (in most cases).
- Be UV-stable (because they sit in the sun).
- Resist hot and cold temperatures over 25-30 years of service
Various hot-melt and reactive adhesives meet these physical characteristics and
perform better than the ambient sealants and adhesives being used today. They
allow manufacturers to produce product faster because they enable faster cycle
times and curing. They are also more cost-effective because they reduce
material consumption. By using the right material and application technique,
manufacturers can use as little as a quarter of the amount of sealant they
Reactive adhesives, for example, provide tremendous, lasting bond strength in
the face of strenuous use and powerful elements, such as moisture and the
intense temperature changes that solar panels must endure. However, the
technology to apply these reactive adhesives hasn’t been widely used in the
solar industry until now.
Because reactive adhesives begin curing as soon as they are exposed, they must
be properly contained and dispensed to prevent premature curing. Without this
proper containment and dispensing, adhesive is wasted and products are not bonded
or sealed correctly.
In addition, new technologies that enable the use of smarter adhesive and
sealant materials also offer the possibility to fully or partially automate,
which can increase a plant’s efficiency and capacity.
The basic industry standard is to express capacity of a plant in megawatt
output per year. For example, 40 MW means the facility can make 40 MW of panels
per year (approximately 350,000 panels, depending on the module technology and
nominal power per module). Some plants can only produce 5 MW of panels because
all production is manual, but other fully-automated plants have exceeded
Large Material Bundles
Being able to choose the most efficient size of material can
be a powerful way for solar manufacturers to reduce costs. Currently, most
manufacturers use either tapes or cartridges, which come in various sizes and
are mostly used in manual or semi-automated application processes.
These materials come with a variety of challenges. First, they force
manufacturers to frequently reload, which interrupts production. Their use can
also result in a loss of quality because applying them is typically a manually
intensive and, therefore, error-prone process.
In addition, tape is expensive to use. To manufacture tape, a supplier either
adds adhesive to the backing that will deliver the adhesive or extrudes
material onto a roll. New technologies save money by allowing solar panel
manufacturers to use liquefied adhesives, thus eliminating that extra step.
All sorts of adhesives, including 1K RTV silicones, hot-melt and reactive
adhesives, are typically offered in larger volumes, which are cheaper due to
the ability to buy and use them in bulk.
Liquid butyl application for side/edge seal is a more cost-efficient form and requires less refilling than traditional butyl tapes.
ApplicationsSide Seal or Edge Seal
Thin-film solar panels usually don’t have the added protection of an actual
frame, making them more susceptible to moisture. In addition, encapsulation is
typically done with EVA, an inadequate moisture barrier. Manufacturers,
therefore, need to add an additional moisture barrier called a side or edge
seal in the perimeter area of the modules.
Butyl is an excellent moisture barrier typically used for side or edge seal in
pre-extruded tape form. When applied as a liquid with new technology rather
than traditional tape, butyl offers an ideal, cost-saving solution.
The pre-extruded butyl tape used today is often applied manually or with tape
robots. This setup forces manufacturers to refill often because of the limited
size of the tape reels. It is also expensive and slow to apply manually.
Furthermore, manual tape application diminishes product quality.
New hot-melt butyl processing technologies allow manufacturers to apply butyl
adhesive in-line and in liquid form. These technologies also allow for more
cost-efficient, larger product sizes that minimize the downtime associated with
All solar panels must have components that provide structure and installation
capability. Since these panels must tolerate constant sun, wind and
precipitation exposure, these components are critical to product performance
and endurance. Because of their different structures, this is accomplished in
very different ways in crystalline and thin-film modules. Fortunately, new
technologies can increase manufacturers’ production efficiencies for both.
On crystalline solar panels, frames provide protection, stable structure and an
installation (or carrier) structure. The frame on crystalline modules is
typically attached in a completely manual or semi-automated process that uses
tape as the adhesive. New technology, however, allows an automated option that
applies a framing sealant around the solar module and replaces labor-intensive,
Thin-film glass-on-glass modules don’t have frames. In fact, they don’t even
have traditional solar cells; photovoltaic material is put on the glass panes
as a thin layer or “film,” hence the name. Thin film panels don’t use a back
sheet; instead, they typically use a back pane of glass. While this structure
makes them stronger, a carrier system still needs to be installed on them, so a
backrail must be attached. A backrail is a piece (or pieces) of metal bonded to
the back that provides support for installation as well as strength against
Although their structures are different, framing and backrailing use similar
technologies and materials, and new automated technologies make both processes
less expensive and faster, moving these module systems closer to grid parity.
New technologies attach frames or backrails using several in-line glue
stations. Like the side-seal application, these technologies allow manufacturers
to apply sealant in liquid form and also enable the use of larger-sized sealant
containers. This means less-frequent refilling, greater production speed and
more cost-efficient material sourcing. These technologies also offer the
possibility of automation, delivering faster cycle times, increased
productivity and reduced costs, in addition to improved product quality.
One of the exciting things about new adhesive and sealant technologies for the solar
industry is that they allow manufacturers to improve product quality and
performance while keeping costs low. For example, frame corners can be weak
spots in the structure that allow moisture ingress. For additional product
quality and durability, many manufacturers seal both the frame corners and the
edges. New automated dispensing technologies make it possible to add this extra
step without adding significant costs.
Junction Box Attachment and
Junction boxes are critical as they are the mechanisms by which energy leaves
the module. However, because junction boxes are often connected to the panel
with tape or tape-supported cold material, their attachment is an expensive,
slow process. In addition, junction box attachment is almost always a manual
process, although it’s actually easy to automate.
Another problem to overcome with junction boxes is that electrical contacts
don’t mix well with water. One way to protect from possible water seepage is by
potting – filling the junction box with a 2K silicone, thus covering the
contacts inside the box. 2K silicones provide the quick curing and proper
leveling required for potting, but are very expensive.
New technologies allow manufacturers to use alternative materials, such as
polyamides or reactive hot melts, that offer an almost instant cure time and
reduce the overall cost of the process.
Advances in encapsulation technology are particularly exciting for solar
applications. A typical crystalline module process involves two encapsulants;
glass comes in first, then an EVA foil sheet is applied. In most cases, the
sheet is pre-cut from a roll or procured as a sheet and placed manually on a
glass pane. Next comes a string or array of solar cells on top, and another EVA
foil sheet is placed atop the solar cells. Finally, the backsheet material goes
on, making a solar sandwich of sorts.
This assembly then goes into a laminator where the whole sandwich, or laminate,
is evacuated (air is removed) and the laminate is heated up. This melts the EVA
foils until they liquefy. Next, pressure is applied. When this package cools
down, an encapsulated solar laminate is formed.
There are several downsides to this process. First, the current lamination
technology is always a batch-type process that consumes a lot of energy and
typically takes about 10-15 minutes per module batch. Laminators offered in the
market can process single modules or up to 10 modules a time, but they still
require the same process time. The only way to go faster is to add more
laminators that have a large footprint and are costly.
The foils present another challenge. They are usually oversized to ensure coverage
of the entire area, so they must be trimmed after lamination. Whether manual or
automated, this requires an expensive series of steps that slows down the line.
Nordson is currently investigating and developing application technologies to apply
the encapsulant material in-line and in liquid form. Not only will this
eliminate the need to hand-cut and trim the foil, it will also speed up the
overall process, allowing increased throughput. The ultimate goal is to
minimize the process time and energy used for lamination, or, ideally, to
eliminate the traditional lamination process altogether.
Parity Can Be a Reality
Solar-panel manufacturing is at a turning point, and grid
parity is getting closer. Even the smallest solar-panel manufacturer can begin
to benefit from these adhesive and sealant advancements. In addition to
incorporation in new solar module production lines, these new technologies
integrate easily into any process and can be used to upgrade existing systems.
These technologies help manufacturers reduce production costs and speed
production by enabling them to use smarter materials and larger-bundle,
industrial sizes in any line. These technologies also offer a cost-effective
way to move toward increased automation that provides significant benefits for
overall efficiency and quality. Even better, these advancements are all
flexible; they can be customized and scaled to meet the specific needs of any
For more information, visit www.nordson.com/solarsolutions.