Types of seasonal thermal storage
Seasonal (or "annualized") thermal storage can be accomplished in several ways:

Solar heat can be directly captured by the structure's spaces (through windows and other surfaces) in summer and then passively transfered (by conduction) through its floors, walls (and, sometimes, roof) into adjoining thermally-sequestered storage masses, as is done by the "Passive Annual Heat Storage" (PAHS) technique, and then passively returned (by conduction and radiation) as those spaces cool in winter.

Or, heat (or heat-generating energy) can be captured by isolated devices and transfered to/deposited (either actively or passively) in the earth (or other storage masses or mediums) adjoining the building, with direct passive return through the structure's elements as the spaces cool, as exemplified by the "Annualized Geo-Solar" (AGS) technique.

Or, heat (or heat-generating energy) can be captured by such isolated devices, transfered to an isolated storage mass or medium, and then actively returned and dispersed as desired to building materials and spaces. This last approach optimizes quick-response "control" options, while the former tend to offer much simpler, far less expensive implementations and less vulnerabilities to equipment failures.

Seasonal thermal stores are also found on a variety of scales, from those installed in individual houses to those serving neighbourhoods via district heating.

Individual structures
Although the use of active seasonal thermal stores dates back to at least 1939 (MIT Solar House #1), The United States, Switzerland and Germany have all been notable pioneers in the use of individual house seasonal heat stores over the years. (Actually, direct passive space-tempering was probably one of the original motivations of early man's movement into caves, as the earth natually "annualizes" temperatures below about 20 feet, and many ancient dwellings of classical Greece and before domonstrate an understanding of passive solar design, orientation and heat-storage mass, as do the cliff-dwellings of the american southwest.)

In the early 1980s, with the growing trend toward more passive solar, three US solar design pioneers demonstrated the simplicity of using thermally and moisture-protected on-site earth as a storage medium, with direct conduction as the heat return method. Daniel Geery's 1982 book, "Solar Greenhouses: Underground" and John Hait's 1983 "Passive Annual Heat Storage" advocated using the building spaces for direct gain solar capture and conduction into adjoining thermally-buffered soil, while Don Stephens posed the alternative of isolated solar gain and ducted deposit into the core of the protected earth mass, utilizing calculated heat-transfer rates through soil to regulate a time-lagged return, six months after deposit. (these concepts are compared in greater detail at: [1])

Perhaps the best known international example of the higher-tech active approach is the experimental “Jenni-Haus” built in 1989 in Oberburg, Switzerland. This has 3 tanks storing a total of 118m³ (4,100 cubic feet) [2] providing far more heat than is required to heat the building.

The more recent “Zero Heating Energy House”, completed in 1997 in Berlin as part of the IEA Task 13 low energy housing demonstration project, stores water at temperatures up to 90°C (195°F) inside a 20m³ (700 cubic feet) tank in the basement [3], and is now one of a growing number of similar properties.

Neighbourhoods
At the neighbourhood level, the Wiggenhausen-Süd solar development at Friedrichshafen has received international attention. This features a 12,000 m³ (424,000 cubic feet) reinforced concrete thermal store linked to 4,300m² (46,000 square feet) of solar collectors, which will supply the 570 houses with around 50% of their heating and hot water [4].

A different approach is illustrated by the Drake Landing Solar Community development in Okotoks, Alberta. Here the store is created from the ground itself, with solar heated water pumped into a Borehole Thermal Energy Storage (BTES) system. This consists of 144 boreholes, each 37m (121 feet) deep, which heat the ground to a maximum of around 90°C (195°F) [5].