Solar Storage Tank Matching: Optimizing Your Solar Water Heating System 

Solar water heating systems are a sustainable and efficient way to reduce energy consumption and lower utility bills. One critical component of these systems is the solar storage tank, which stores the heated water until it's needed. Selecting the right storage tank is crucial for the system's performance and longevity. 

Types of Solar Storage Tanks 

Pressurized Tanks 

Pressurized tanks are commonly used in solar water heating systems. They are designed to withstand high pressures and are typically made from materials like stainless steel or glass-lined steel to prevent corrosion.

Non-Pressurized Tanks 

Non-pressurized tanks, also known as atmospheric tanks, operate at atmospheric pressure and are often used in olar heating system systems. These tanks are less expensive than pressurized tanks of similar volume. Some options are able to be easily disassembled and reassembled allowing large volumes of storage for solar heating system systems to pass though doorways without deconstruction costs that can be associated with pressurized tanks.

Tank Materials 

Stainless Steel: Offers high durability and corrosion resistance but is more expensive. 

• Data Point: Stainless steel tanks typically last 15-20 years with minimal maintenance. 

Glass-Lined: Provides good corrosion resistance at a lower cost but the glass lining can be compromised over many cycles of extreme temperature changes.

• Data Point: Glass-lined tanks have an average lifespan of 10-15 years. 

Factors Influencing Tank Selection 

1. System Size and Hot Water Demand: 

• Larger tanks are required for higher hot water demands. 

• Data Point: A typical household of four people requires a tank capacity of around 80-100 gallons. 

2. Climate Considerations: 

• Cold climates may require better-insulated tanks to prevent heat loss. 

• Data Point: Tanks in colder climates often use additional insulation, such as polyurethane foam, to achieve R-values of 16 or higher. 

3. Space and Installation Constraints: 

• Available space can limit the size and type of tank. 

• Installation complexity can also impact tank choice. 

4. Budget Considerations: 

• Higher quality tanks often have higher upfront costs but can offer better long-term savings through improved efficiency and durability. 

Solar Tank Sizing 

Solar tank sizing generally falls under two criteria: 

1. Daily Hot Water Usage/Load: 

• This is determined based on the amount of daily hot water usage for a residential, commercial, or industrial property. 

• Many organizations (IAPMO, ASHRAE, ASPE, and others) provide sizing tables to estimate hot water usage for specific properties. 

2. Tank Volume to Solar Collectors Ratio: 

• Generally, the ratio of collector area(ft^2) to tank volume(gal) is at least 50%. 

Economics: 

Undersized Tank: 

• Solar savings may not be adequate as the tank reaches its maximum set temperature, shutting the system off and losing potential solar production. 

Oversized Tank: 

• Initial cost may be prohibitive.

System Performance: 

Undersized Tank: 

• Can reach higher temperatures early in the day, impacting the system’s life expectancy over time and limiting the amount of energy than can be stored by the tank. 

Oversized Tank: 

• Does not provide higher water temperatures required but increases overall energy collected due to lower fluid temperature efficiencies. It can capture intermittent high solar input periods, as occurs with varying weather conditions during the day. 

Matching Tanks with Solar Water Heating Systems 

Compatibility with Solar Collectors 

Different types of solar collectors (e.g., flat plate, evacuated tube) have specific requirements for optimal performance. Ensuring the tank is compatible with the collector type is crucial.

Heat Exchanger Integration 

Many solar storage tanks come with built-in heat exchangers to transfer the heat from the solar collectors to the water. Matching the tank’s heat exchanger with the system’s needs is essential for efficient operation. 

Insulation and Efficiency Ratings 

Tanks with higher insulation ratings will retain heat more effectively, reducing energy loss and improving system efficiency. The U.S. Department of Energy (DOE) recommends looking for tanks with an insulation R-value of at least 16 to maximize energy savings. 

SunEarth Empire Series Collectors 

Often paired with glass lined pressurized tanks for residential systems, these systems can achieve efficiencies of up to 90%, significantly reducing annual water heating costs. According to SunEarth, the Empire Series collectors are designed to deliver maximum efficiency in residential applications when paired with high-quality pressurized tanks. 

SunEarth ThermoRay Series 

These collectors can be matched with non-pressurized tanks for large-scale commercial installations. Commercial systems using ThermoRay collectors have been shown to provide hot water temperatures consistently above 140°F, even in colder climates. SunEarth states that their ThermoRay Series is engineered for robust commercial performance, ensuring reliable hot water delivery in demanding environments. 

SunEarth Storage Tanks 

SunEarth offers a variety of storage tanks, including both pressurized and non-pressurized options, tailored to meet specific system requirements. SunEarth's tanks are known for their superior insulation and long-term durability, contributing to overall system efficiency. 

Performance metrics for these pairings show significant energy savings and high efficiency, making them a popular choice for both residential and commercial applications. 

Other Viable Sources and Best Practices 

When selecting a solar storage tank, consider references from other reputable manufacturers and products. Look for industry standards and certifications like UL for assurance of quality and performance. The UL emphasizes that certified solar water heating systems and storage tanks are tested rigorously to ensure they meet or exceed performance and safety standards.

Best Practices: 

• Regular maintenance checks to ensure the system's efficiency and longevity. 
• Monitoring system performance to detect and address issues promptly. 

Choosing the right solar storage tank is vital for maximizing the efficiency and lifespan of your solar water heating system. Consider all factors, including system size, climate, and budget, to make an informed decision. Consulting with a professional can also ensure that your system is designed and installed correctly for optimal performance. 

 

Sources: 

Solar Energy Industries Association (SEIA). "Benefits of Solar Water Heating." 

International Renewable Energy Agency (IRENA). "Solar Heating Systems and Non-Pressurized Tanks." 

American Council for an Energy-Efficient Economy (ACEEE). "Solar Water Heating: Types and Benefits." 

U.S. Department of Energy (DOE). "Insulation and Efficiency for Solar Water Heaters." 

Solar Rating & Certification Corporation (SRCC). "Certification Standards for Solar Water Heating Systems." 

SunEarth. "Product Specifications and Performance Data."