SOLAR FLOATIE DESIGN
Insights on the design of the low-cost solar concentrator
THE SOLAR FLOATIE
A low-cost solar concentrator
The Solar Floatie is a solar home system that aims to provide affordable heating and electrical power for homeowners, farmers, and workers in El Norte Chico, Chile. The system implements the principles of concentrating photovoltaics to harness the sun’s energy and converts it into useful electrical power. The novelty of this system is in its replacement of conventionally high-cost, industrial components with low cost, accessible materials. Major high cost points in conventional concentrators include the reflective mirror component and metal structural support. This has been replaced with reflective aluminized mylar, and the structure was eliminated with an inflatable design, reducing the overall cost of the system of a concentrator by 2 magnitudes.
FEATURES
HALF ACCEPTANCE ANGLE OF 12°
Higher due to our unique design compared to traditional systems which would require more accurate tracking - up to 1°
$1.95 CAD/W
Final cost of the system is $1.95 CAD/W, or $0.047 CAD/kWh for the levelized cost of electricity. This is two magnitudes lower than traditional cogeneration systems.
DESIGNED FOR YOUR HOME
Two units are able to provide a user with enough electricity to power LEDs, electronics, and a cooker, equating to 700 Wh/day.
86% HEAT RECOVERY
Recovering heat from the solar cell cools it to ensure that the performance is not compromised, and uses energy that would otherwise go to waste. The heat system can use the recovered heat in applications such as radiative floor heating, air conditioning, in residential piping needs, and for cooking.
THE DESIGN JOURNEY
Insights of our journey and design
THE PROBLEM
Overview
Affordable and clean energy is one of the global challenges set by the UN Sustainable Development Goals to improve the livelihood of many people. Despite the acceleration of technology today, according to the United Nations, 800 million people remain without electricity.
Off-grid communities in isolated areas, such as in El Norte Chico, Chile, face a greater challenge in getting their energy needs for space heating, air conditioning, and power. Urban communities in Chile tend to have over 93% of electrification, whereas rural and off-grid communities have a smaller percentage due to financial barriers for local communities and homemakers. Homemakers typically have trouble with space heating due to residential buildings dissipating heat quickly through their roofs, resulting in cold winter nights and hot summer days, making energy use high and expensive in winter and summer. Furthermore, many farmers with solar farms experience trouble with producing energy on the grid due to errors in dissipation. These farms tend to not have the capacity to have both electrical and heating capabilities due to the expenses of electricity afterwards, as well as physical capacity on their roofs.
Based on the variety of stakeholders discussed, a solution is required for affordable and accessible ways to meet their specific energy needs.
THE CURRENT TECHNOLOGIES
Using the design thinking process, we found literature stating low adoption of solar technologies due to “high installation costs”. These costs can be due to the cost of several arrays of solar panels and the tracking device needed to maximize the solar input. M. Ali’s research concludes that people living in rural areas would benefit greatly from increased electrification if solar home system efficiency and performance can be improved in a costly manner that would allow the users to adapt the system to their needs. As such, we came to the conclusion that the problem with solar energy technologies in the chosen community was due to lack of access, costly systems, and unreliability, resulting in poor implementation in different communities.
From our research, solar concentrators are a common method to increase efficiency and reduce the cost of photovoltaic systems. Current solar concentrators are developed for high scale, industrial applications, typically made of expensive materials such as metals and mirrors to operate. This led to different design considerations to create a low-cost system, as well as a system that would be easy to manufacture with respect to the industrial manufacturing counterpart.
In the following design decisions, we used principles of Design for Manufacturing, Design for Sustainability (Feron), and Human-Centred Design.
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LOW-COST DESIGN
The first thing we did was deconstruct the collector such that high cost points, such as mirrors, can be replaced with reflective polymers, such as mylar, which has greater than 90% reflectivity. However, mylar is a polymer film with little to no structural support, another high cost metric. Thus, we decided on an inflated design in order to keep the low cost yet effective material, while maintaining structure.
GEOMETRY & MANUFACTURING
The geometry of this concentrator was by far the largest challenge. Our first design was based on a large beach ball and was spherical in shape. However, this turned out to be very difficult to manufacture due to the quality of bonding at the mylar and ball seam (due to the spherical nature). The final design features a discretized compound parabolic concentrator, which was easy to manufacture, has a large half acceptance angle (~12 degrees) resulting in a simple dual axis system (a ball and socket joint and a pinhole sun finder) that is easy to use and accessible for the user. The high acceptance angle also means that the user does not have to adjust the system often.
INTERFACES
The spherical designs presented challenges in the placement of the solar cell and the required interfaces, as it would likely cause a mass imbalance and compromise the concentration. With the final CPC geometry, the receiver would be at the bottom of the system, which would not affect the concentrator. Thus, the heat sink was designed at the base of the system, which would encompass the major design challenges of the system: it allowed for an airtight seal and a means for inflation, had a universal attachment to any common ball and socket joint available for tracking, connected the solar cell to the heat recovery system, and did not counterbalance the overall structure. This alleviated many of the challenges our inflated design presented in a sleek, elegant design.
TRACKING
The challenge with tracking systems was dependent on the cost and accuracy needed for the system. With the new geometry, there was a higher acceptance angle, decreasing the number of adjustments needed for tracking. The manual dual axis tracking system, which consists of a ball and socket joint and a pinhole tracker for an accurate and easy method for users to track the sun for maximum electrical output.
